Huawei AR Series Access Routers

CLI-based Configuration Guide - IP Unicast Routing 9 BGP Configuration

9 BGP Configuration

About This Chapter

The Border Gateway Protocol (BGP) is used between Autonomous Systems (ASs)
to transmit routing information. BGP applies to large and complex networks.

9.1 Overview of BGP

9.2 Understanding BGP
9.3 Summary of BGP Configuration Tasks
9.4 Licensing Requirements and Limitations for BGP
9.5 Default Settings for BGP
9.6 Configuring Basic BGP Functions
Before building a BGP network, you need to configure basic BGP functions.
9.7 Configuring BGP Security
Configuring connection authentication and BGP GTSMfor BGP peers can improve
BGP network security.
9.8 Simplifying IBGP Network Connections
Configuring a route reflector and a confederation on an IBGP network can simplify
IBGP network connections.
9.9 Configuring BGP Route Selection and Load Balancing
BGP has many route attributes. These attributes can be configured to change the
route selection result.
9.10 Controlling the Receiving and Advertisement of BGP Routes
Controlling the receiving and advertisement of BGP routes can reduce the routing
table size and improve network security.
9.11 Adjusting the BGP Network Convergence Speed
You can configure BGP timers, disable rapid EBGP connection reset, and configure
BGP route dampening to speed up BGP network convergence and improve BGP
security.
9.12 Configuring BGP Reliability

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You can configure BGP Tracking, association between BGP and BFD, and BGP GR
to speed up BGP network convergence and improve BGP reliability.
9.13 Configuring BGP Route Summarization
On IPv4 networks, BGP supports automatic route summarization and manual
route summarization. Manual route summarization takes precedence over
automatic route summarization. On IPv6 networks, BGP supports only manual
route summarization.
9.14 Configuring On-demand Route Advertisement
If a BGP device only wants to received required routes but its peer cannot
maintain different export policies for connected devices, you can configure prefix-
based BGP outbound route filtering (ORF) to meet this requirement.
9.15 Configuring BGP to Advertise Default Routes to Peers
If a BGP device needs to send multiple routes to its peer, the BGP device can be
configured to send only a default route with the local address as the next-hop
address to its peer, regardless of whether there are default routes in the local
routing table. This function reduces the number of network routes and saves
memory and network resources.
9.16 Configuring Path MTU Auto Discovery
BGP path maximum transmission unit (MTU) auto discovery can discover the
minimum MTU (path MTU) on the network path from the source to the
destination so that TCP can transmit BGP messages based on the path MTU.
9.17 Configuring MP-BGP
Multiprotocol BGP (MP-BGP) enables BGP to support IPv4 unicast networks, IPv4
multicast networks, and IPv6 unicast networks.
9.18 Configuring the Dynamic BGP Peer Function
9.19 Maintaining BGP
9.20 Configuration Examples for BGP
9.21 FAQ About BGP

9.1 Overview of BGP

Definition
The Border Gateway Protocol (BGP) is a distance vector protocol that allows
devices between Autonomous Systems (ASs) to communicate and selects optimal
routes. BGP-1, BGP-2, and BGP-3 are three earlier versions of BGP. BGP-4 has been
used since 1994. Since 2006, unicast IPv4 networks have been using BGP-4, and
other networks (such as IPv6 networks) have been using MP-BGP.
MP-BGP is an extension of BGP-4 and applies to different networks; however, the
original message exchange and routing mechanisms of BGP-4 are not changed.
MP-BGP applications on IPv6 unicast and IPv4 multicast networks are called
BGP4+ and Multicast BGP (MBGP) respectively.

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Purpose
A network is divided into different ASs to facilitate the management over the
network. In 1982, the Exterior Gateway Protocol (EGP) was used to dynamically
exchange routing information between ASs. EGP advertises only reachable routes
but not select optimal routes or prevent routing loops. Therefore, EGP cannot
meet network management requirements.

BGP was designed to replace EGP. Different from EGP, BGP can select optimal
routes, prevent routing loops, transmit routing information efficiently, and
maintain a large number of routes.

Although BGP is used to transmit routing information between ASs, BGP is not the
best choice in some scenarios. For example, on the egress connecting a data
center to the Internet, static routing instead of BGP is used to prevent a huge
number of Internet routes from affecting the internal network of the data center.

Benefits
BGP ensures high network security, flexibility, stability, reliability, and efficiency:
● BGP uses authentication and Generalized TTL Security Mechanism (GTSM) to
ensure network security.
● BGP provides routing policies to allow for flexible route selection and
routing policy-based route advertisement.
● BGP provides 9.2.8 Route Summarization and 9.2.9 Route Dampening to
prevent route flapping and improve network stability.
● BGP uses the Transport Control Protocol (TCP) with port number 179 as the
transport layer protocol and supports 9.2.10 BFD for BGP, 9.2.11 BGP
Tracking, and 9.2.12 BGP GR and NSR to improve network reliability.
● BGP uses the 9.2.14 Dynamic Update Peer-Groups technology to send
packets in groups when a large number of peers and routes exist and most
peers share the same outbound policies, improving BGP forwarding
performance.

9.2 Understanding BGP

9.2.1 Basic Concepts of BGP

Autonomous System
An Autonomous System (AS) is a group of Internet Protocol (IP) networks that are
controlled by one entity, typically an Internet service provider (ISP), and that have
the same routing policy. Each AS is assigned a unique AS number, which identifies
an AS on a BGP network. Two types of AS numbers are available: 2-byte AS
numbers and 4-byte AS numbers. A 2-byte AS number ranges from 1 to 65535,
and a 4-byte AS number ranges from 1 to 4294967295. Devices supporting 4-byte
AS numbers are compatible with devices supporting 2-byte AS numbers.

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BGP Neighbor Type

As shown in Figure 9-1, BGP neighbor type is classified into two types according
to where it runs: External BGP (EBGP) and Internal BGP (IBGP).

Figure 9-1 BGP operating mode

AS200

IBGP
EBGP EBGP

AS100 AS300

Internet

● EBGP: runs between ASs. To prevent routing loops between ASs, a BGP device
discards the routes with the local AS number when receiving the routes from
EBGP peers.
● IBGP: runs within an AS. To prevent routing loops within an AS, a BGP device
does not advertise the routes learned from an IBGP peer to the other IBGP
peers and establishes full-mesh connections with all the IBGP peers. To
address the problem of too many IBGP connections between IBGP peers, BGP
uses 9.2.6 Route Reflector and 9.2.7 BGP Confederation.
NOTE
If a BGP device needs to advertise the route received from an EBGP peer outside an AS
through another BGP device, IBGP is recommended.

Device Roles in BGP Message Exchange

There are two device roles in BGP message exchange:
● Speaker: The device that sends BGP messages is called a BGP speaker. The
speaker receives and generates new routes, and advertises the routes to other
BGP speakers.
● Peer: The speakers that exchange messages with each other are called BGP
peers. A group of peers can form a peer group.

BGP Router ID
The BGP router ID is a 32-bit value that is often represented by an IPv4 address to
identify a BGP device. It is carried in the Open message sent during the

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establishment of a BGP session. When two BGP peers need to establish a BGP
session, they each require a unique router ID. Otherwise, the two peers cannot
establish a BGP session.
The BGP router ID of a device must be unique on a BGP network. It can be
manually configured or selected from IPv4 addresses on the device. By default, an
IPv4 address of a loopback interface on a device is used as the BGP router ID. If no
loopback interface is configured on the device, the system selects the largest IPv4
address from all IPv4 addresses of interfaces as the BGP router ID. Once the BGP
router ID is selected, the system retains this router ID even if a larger IPv4 address
is configured on the device later. The system changes the BGP router ID only when
the corresponding IPv4 address is deleted.

9.2.2 BGP Fundamentals

BGP peer establishment, update, and deletion involve five types of messages, six
state machine states, and five route exchange rules.

BGP Messages
BGP peers exchange the following messages, among which Keepalive messages
are periodically sent and other messages are triggered by events.
● Open message: is used to establish BGP peer relationships.
● Update message: is used to exchange routes between BGP peers.
● Notification message: is used to terminate BGP connections.
● Keepalive message: is used to maintain BGP connections.
● Route-refresh message: is used to request the peer to resend routes if routing
policies are changed. Only the BGP devices supporting route-refresh can send
and respond to Route-refresh messages.

BGP State Machine

As shown in Figure 9-2, a BGP device uses a finite state machine (FSM) to
determine its operations with peers. The FSM has six states: Idle, Connect, Active,
OpenSent, OpenConfirm, and Established. Three common states are involved in
BGP peer establishment: Idle, Active, and Established.

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Figure 9-2 BGP state machine

Idle

Connect Retry Start

Timeout
Error
Connect
TCP Failed
TCP
Active Established

Error
OpenSent
TCP
Established Receive
Correct Open
Error
OpenConfirm

Receive Correct
Keepalive
Error
Established

1. The Idle state is the initial BGP state. In Idle state, the BGP device refuses all
connection requests from neighbors. The BGP device initiates a TCP
connection with its BGP peer and changes its state to Connect only after
receiving a Start event from the system.
NOTE

● The Start event occurs when an operator configures a BGP process or resets an
existing BGP process, or when the router software resets a BGP process.
● If an error occurs at any state of the FSM, for example, the BGP device receives a
Notification message or TCP connection termination notification, the BGP device
returns to the Idle state.
2. In Connect state, the BGP device starts the ConnectRetry timer and waits to
establish a TCP connection.
– If the TCP connection is established, the BGP device sends an Open
message to the peer and changes to the OpenSent state.
– If the TCP connection fails to be established, the BGP device moves to the
Active state.
– If the BGP device does not receive a response from the peer before the
ConnectRetry timer expires, the BGP device attempts to establish a TCP
connection with this peer and stays in Connect state.
3. In Active state, the BGP device keeps trying to establish a TCP connection with
the peer.

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– If the TCP connection is established, the BGP device sends an Open

message to the peer, closes the ConnectRetry timer, and changes to the
OpenSent state.
– If the TCP connection fails to be established, the BGP device stays in the
Active state.
– If the BGP device does not receive a response from the peer before the
ConnectRetry timer expires, the BGP device returns to the Connect state.
4. In OpenSent state, the BGP device waits an Open message from the peer and
then checks the validity of the received Open message, including the AS
number, version, and authentication password.
– If the received Open message is valid, the BGP device sends a Keepalive
message and changes to the OpenConfirm state.
– If the received Open message is invalid, the BGP device sends a
Notification message to the peer and returns to the Idle state.
5. In OpenConfirm state, the BGP device waits for a Keepalive or Notification
message from the peer. If the BGP device receives a Keepalive message, it
transitions to the Established state. If it receives a Notification message, it
returns to the Idle state.
6. In Established state, the BGP device exchanges Update, Keepalive, Route-
refresh, and Notification messages with the peer.
– If the BGP device receives a valid Update or Keepalive message, it
considers that the peer is working properly and maintains the BGP
connection with the peer.
– If the BGP device receives an invalid Update or Keepalive message, it
sends a Notification message to the peer and returns to the Idle state.
– If the BGP device receives a Route-refresh message, it does not change its
status.
– If the BGP device receives a Notification message, it returns to the Idle
state.
– If the BGP device receives a TCP connection termination notification, it
terminates the TCP connection with the peer and returns to the Idle state.

Route Exchange Rules

A BGP device adds optimal routes to the BGP routing table to generate BGP
routes. After establishing a BGP peer relationship with a neighbor, the BGP device
follows the following rules to exchange routes with the peer:

● Advertises the BGP routes received from IBGP peers only to its EBGP peers.
● Advertises the BGP routes received from EBGP peers to its EBGP peers and
IBGP peers.
● Advertises the optimal route to its peers when there are multiple valid routes
to the same destination.
● Sends only updated BGP routes when BGP routes change.
● Accepts all the routes sent from its peers.

9.2.3 Interaction Between BGP and an IGP

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BGP and IGPs use different routing tables. To enable different ASs to
communicate, you need to configure interaction between BGP and IGPs so that
BGP routes can be imported into IGP routing tables and IGP routes can also be
imported to BGP routing tables.

Importing IGP Routes to BGP Routing Tables

BGP does not discover routes and so needs to import the routes discovered by
IGPs to BGP routing tables so that different ASs can communicate. When an AS
needs to advertise routes to another AS, an Autonomous System Boundary Router
(ASBR) imports IGP routes to its BGP routing table. To better plan the network,
you can use routing policies to filter routes and set route attributes when BGP
imports IGP routes. Alternatively, you can set the multi-exit discriminator (MED)
to help EBGP peers select the best path for traffic entering an AS.
BGP imports routes in either import or network mode:
● In import mode, BGP imports IGP routes, including RIP, OSPF, and IS-IS routes,
into BGP routing tables based on protocol type. To ensure the validity of
imported IGP routes, BGP can also import static routes and direct routes in
import mode.
● In network mode, BGP imports the routes in the IP routing table one by one
to BGP routing tables. The network mode is more accurate than the import
mode.

Importing BGP Routes to IGP Routing Tables

When an AS needs to import routes from another AS, an ASBR imports BGP routes
to its IGP routing table. To prevent a large number of BGP routes from affecting
devices within the AS, IGPs can use routing policies to filter routes and set route
attributes when importing BGP routes.

9.2.4 BGP Security

BGP uses authentication and Generalized TTL Security Mechanism (GTSM) to
ensure exchange security between BGP peers.

BGP Authentication
BGP authentication includes Message Digest 5 (MD5) authentication and keychain
authentication, which improves communication security between BGP peers. In
MD5 authentication, you can only set the authentication password for a TCP
connection. In keychain authentication, you can set the authentication password
for a TCP connection and authenticate BGP messages.

BGP GTSM
BGP GTSM checks whether the time to live (TTL) value in the IP packet header is
within a predefined range and permits or discards the packets of which the TTL
values are out of the predefined range to protect services above the IP layer. BGP
GTSM enhances system security.
Assume that the TTL value range of packets from BGP peers is set to 254-255.
When an attacker forges valid BGP packets and keeps sending these packets to

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attack a device, the TTL values of these packets are smaller than 254. If BGP
GTSM is not enabled on the device, the device finds that these packets are
destined for itself and sends the packets to the control plane for processing. Then
the control layer needs to process a large number of such attack packets, causing
high CPU usage. If BGP GTSM is enabled on the device, the system checks the TTL
values in all BGP packets and discards the attack packets of which the TTL values
are smaller than 254. This prevents network attack packets from consuming CPU
resources.

9.2.5 BGP Route Selection Rules and Load Balancing

There may be multiple routes to the same destination in a BGP routing table. BGP
will select one route as the optimal route and advertise it to peers. To select the
optimal route among these routes, BGP compares the BGP attributes of the routes
in sequence based on route selection rules.

BGP Attributes
Route attributes describe routes. BGP route attributes are classified into the
following types. Table 9-1 lists common BGP attributes.
● Well-known mandatory attribute
All BGP devices can identify this type of attributes, which must be carried in
Update messages. Without this type of attributes, errors occur in routing
information.
● Well-known discretionary attribute
All BGP devices can identify this type of attributes, which are optional in
Update messages. Without this type of attributes, errors do not occur in
routing information.
● Optional transitive attribute
BGP devices may not identify this type of attributes but still accepts them and
advertises them to peers.
● Optional non-transitive attribute
BGP devices may not identify this type of attributes. If a BGP device does not
identify this type of attributes, it ignores them and does not advertise them to
peers.

Table 9-1 Common BGP attributes

Attribute Type

Origin Well-known mandatory

AS_Path Well-known mandatory

Next_Hop Well-known mandatory

Local_Pref Well-known discretionary

Community Optional transitive

MED Optional non-transitive

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Attribute Type

Originator_ID Optional non-transitive

Cluster_List Optional non-transitive

The following describes common BGP route attributes:

● Origin
The Origin attribute defines the origin of a route and marks the path of a
BGP route. The Origin attribute is classified into three types:
– IGP
A route with IGP as the Origin attribute is of the highest priority. The
Origin attribute of the routes imported into a BGP routing table using the
network command is IGP.
– EGP
A route with EGP as the Origin attribute is of the secondary highest
priority. The Origin attribute of the routes obtained through EGP is EGP.
– Incomplete
A route with Incomplete as the Origin attribute is of the lowest priority.
The Origin attribute of the routes learned by other means is Incomplete.
For example, the Origin attribute of the routes imported by BGP using
the import-route command is Incomplete.
● AS_Path
The AS_Path attribute records all the ASs that a route passes through from
the source to the destination in the vector order. To prevent inter-AS routing
loops, a BGP device does not receive the routes of which the AS_Path list
contains the local AS number.
When a BGP speaker advertises an imported route:
– If the route is advertised to EBGP peers, the BGP speaker creates an
AS_Path list containing the local AS number in an Update message.
– If the route is advertised to IBGP peers, the BGP speaker creates an
empty AS_Path list in an Update message.
When a BGP speaker advertises a route learned in the Update message sent
by another BGP speaker:
– If the route is advertised to EBGP peers, the BGP speaker adds the local
AS number to the leftmost of the AS_Path list. According to the AS_Path
list, the BGP speaker that receives the route can learn about the ASs
through which the route passes to reach the destination. The number of
the AS that is nearest to the local AS is placed on the top of the AS_Path
list. The other AS numbers are listed according to the sequence in which
the route passes through ASs.
– If the route is advertised to IBGP peers, the BGP speaker does not change
the AS_Path attribute of the route.
● Next_Hop
The Next_Hop attribute records the next hop that a route passes through. The
Next_Hop attribute of BGP is different from that of an IGP because it may not

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be the neighbor IP address. A BGP speaker processes the Next_Hop attribute

based on the following rules:
– When advertising a route to an EBGP peer, a BGP speaker sets the
Next_Hop attribute of the route to the address of the local interface
through which the BGP peer relationship is established with the peer.
– When advertising a locally originated route to an IBGP peer, the BGP
speaker sets the Next_Hop attribute of the route to the address of the
local interface through which the BGP peer relationship is established
with the peer.
– When advertising a route learned from an EBGP peer to an IBGP peer, the
BGP speaker does not change the Next_Hop attribute of the route.
● Local_Pref
The Local_Pref attribute indicates the BGP preference of a device and helps
determine the optimal route when traffic leaves an AS. When a BGP device
obtains multiple routes to the same destination address but with different
next hops from different IBGP peers, the BGP device prefers the route with the
highest Local_Pref. The Local_Pref attribute is exchanged only between IBGP
peers and is not advertised to other ASs. The Local_Pref attribute can be
manually configured. If no Local_Pref attribute is configured for a route, the
Local_Pref attribute of the route uses the default value 100.
● MED
The multi-exit discriminator (MED) attribute helps determine the optimal
route when traffic enters an AS. When a BGP device obtains multiple routes
to the same destination address but with different next hops from EBGP
peers, the BGP device selects the route with the smallest MED value as the
optimal route.
The MED attribute is exchanged only between two neighboring ASs. The AS
that receives the MED attribute does not advertise it to any other ASs. The
MED attribute can be manually configured. If no MED attribute is configured
for a route, the MED attribute of the route uses the default value 0.
● Community
The Community attribute identifies the BGP routes with the same
characteristics, simplifies the applications of routing policies, and facilitates
route maintenance and management.
The Community attribute includes self-defined community attributes and
well-known community attributes. Table 9-2 lists well-known community
attributes.

Table 9-2 Well-known community attributes

Community Value Description

Attribute

Internet 0 A BGP device can advertise the

(0x00000000) received route with the Internet
attribute to all peers.

No_Advertise 4294967042 A BGP device does not advertise the

(0xFFFFFF02) received route with the No_Advertise
attribute to any peer.

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Community Value Description

Attribute

No_Export 4294967041 A BGP device does not advertise the

(0xFFFFFF01) received route with the No_Export
attribute to devices outside the local
AS.

No_Export_Subc 4294967043 A BGP device does not advertise the

onfed (0xFFFFFF03) received route with the
No_Export_Subconfed attribute to
devices outside the local AS or to
devices outside the local sub-AS.

● Originator_ID and Cluster_List

The Originator_ID attribute and Cluster_List attribute help eliminate loops in
route reflector scenarios. For details, see 9.2.6 Route Reflector.

BGP Route Selection Policies

When there are multiple routes to the same destination, BGP compares the
following attributes in sequence to select the optimal route:

1. Prefers the route with the largest PrefVal value.

The PrefVal attribute is a Huawei proprietary attribute and is valid only on the
device where it is configured.
2. Prefers the route with the highest Local_Pref.
If a route does not have the Local_Pref attribute, the Local_Pref attribute of
the route uses the default value 100.
3. Prefers the manually summarized route, automatically summarized route,
route imported using the network command, route imported using the
import-route command, and route learned from peers. These routes are in
descending order of priority.
4. Prefers the route with the shortest AS_Path.
5. Prefers the route with the lowest origin type. IGP is lower than EGP, and EGP
is lower than Incomplete.
6. Prefers the route with the lowest MED if routes are received from the same
AS.
7. Prefers EBGP routes, IBGP routes, LocalCross routes, and RemoteCross routes,
which are listed in descending order of priority.
LocalCross allows a PE to add the VPNv4 route of a VPN instance to the
routing table of the VPN instance if the export RT of the VPNv4 route
matches the import RT of another VPN instance on the PE. RemoteCross
allows a local PE to add the VPNv4 route learned from a remote PE to the
routing table of a VPN instance on this local PE if the export RT of the VPNv4
route matches the import RT of the VPN instance.
8. Prefers the route with the lowest IGP metric to the BGP next hop.

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NOTE

If there are multiple routes to the same destination, an IGP calculates the route metric
using its routing algorithm.
9. Prefers the route with the shortest Cluster_List.
10. Prefers the route advertised by the device with the smallest router ID.
If a route carries the Originator_ID attribute, BGP prefers the route with the
smallest Originator_ID without comparing the router ID.
11. Prefers the route learned from the peer with the lowest IP address.

BGP Load Balancing

When there are multiple equal-cost routes to the same destination, you can
perform load balancing among these routes to load balance traffic. Equal-cost
BGP routes can be generated for traffic load balancing only when the first eight
route attributes described in "BGP Route Selection Policies" are the same.

9.2.6 Route Reflector

To ensure connectivity between IBGP peers, you need to establish full-mesh
connections between IBGP peers. If there are n devices in an AS, n(n-1)/2 IBGP
connections need to be established. When there are a large number of devices,
many network resources and CPU resources are consumed. A route reflector (RR)
can be used between IBGP peers to solve this problem.

Roles in RR
As shown in Figure 9-3, the following roles are involved in RR scenarios in an AS.

Figure 9-3 Networking diagram of the RR

Non-
Route Reflector
Client
IBGP IBGP

Client1
Cluster1 IBGP
IBGP

AS65000
Client2 Client3

● Route reflector (RR): a BGP device that can reflect the routes learned from an
IBGP peer to other IBGP peers. An RR is similar to a designated router (DR) on
an OSPF network.
● Client: an IBGP device of which routes are reflected by the RR to other IBGP
devices. In an AS, clients only need to directly connect to the RR.

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● Non-client: an IBGP device that is neither an RR nor a client. In an AS, a non-

client must establish full-mesh connections with the RR and all the other non-
clients.
● Originator: is a device that originates routes in an AS. The Originator_ID
attribute helps eliminate routing loops in a cluster.
● Cluster: is a set of the RR and clients. The Cluster_List attribute helps
eliminate routing loops between clusters.

RR Principles
Clients in a cluster only need to exchange routing information with the RR in the
same cluster. Therefore, clients only need to establish IBGP connections with the
RR. This reduces the number of IBGP connections in the cluster. As shown in
Figure 9-3, in AS 65000, Cluster1 is comprised of an RR and three clients. The
number of IBGP connections in AS 65000 is then reduced from 10 to 4, which
simplifies the device configuration and reduces the loads on the network and CPU.

The RR allows a BGP device to advertise the BGP routes learned from an IBGP
peer to other IBGP peers, and uses the Cluster_List and Originator_ID attributes to
eliminate routing loops. The RR advertises routes to IBGP peers based on the
following rules:

● The RR advertises the routes learned from a non-client to all the clients.
● The RR advertises the routes learned from a client to all the other clients and
all the non-clients.
● The RR advertises the routes learned from an EBGP peer to all the clients and
non-clients.

Cluster_List Attribute
An RR and its clients form a cluster, which is identified by a unique cluster ID in an
AS. To prevent routing loops between clusters, an RR uses the Cluster_List
attribute to record the cluster IDs of all the clusters that a route passes through.

● When a route is reflected by an RR for the first time, the RR adds the local
cluster ID to the top of the cluster list. If there is no cluster list, the RR creates
a Cluster_List attribute.
● When receiving an updated route, the RR checks the cluster list of the route. If
the cluster list contains the local cluster ID, the RR discards the route. If the
cluster list does not contain the local cluster ID, the RR adds the local cluster
ID to the cluster list and then reflects the route.

Originator_ID Attribute
The originator ID identifies the originator of a route and is generated by an RR to
prevent routing loops in a cluster. Its value is the same as the router ID.

● When a route is reflected by an RR for the first time, the RR adds the
Originator_ID attribute to this route. The Originator_ID attribute identifies the
originator of the route. If the route contains the Originator_ID attribute, the
RR retains this Originator_ID attribute.

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● When a device receives a route, the device compares the originator ID of the
route with the local router ID. If they are the same, the device discards the
route.

Backup RR
To ensure network reliability and prevent single points of failures, redundant RRs
are required in a cluster. An RR allows a BGP device to advertise the routes
received from an IBGP peer to other IBGP peers. Therefore, routing loops may
occur between RRs in the same cluster. To solve this problem, all the RRs in the
cluster must use the same cluster ID.

Figure 9-4 Backup RR

RR1 RR2
IBGP

Cluster

IBGP IBGP IBGP

Client1 Client2 Client3

AS65000

As shown in Figure 9-4, RR1 and RR2 reside in the same cluster and have the
same cluster ID configured.

● When Client1 receives an updated route from an EBGP peer, Client1 advertises
this route to RR1 and RR2 using IBGP.
● After RR1 and RR2 receive this route, they add the local cluster ID to the top
of the cluster list of the route and then reflect the route to other clients
(Client2 and Client3) and to each other.
● After RR1 and RR2 receive the reflected route from each other, they check the
cluster list of the route, finding that the cluster list contains their local cluster
IDs. RR1 and RR2 discard this route to prevent routing loops.

RRs of Multiple Clusters in an AS

There may be multiple clusters in an AS. RRs of the clusters establish IBGP peer
relationships. When RRs reside at different network layers, an RR at the lower
network layer can be configured as a client to implement hierarchical RR. When
RRs reside at the same network layer, RRs of different clusters can establish full-
mesh connections to implement flat RR.

Hierarchical RR

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Figure 9-5 Hierarchical RR

ISP

EBGP EBGP

RR-1 RR-1

Cluster1 Client/RR-2
Client
Cluster2

AS100
Client Client

In practice, hierarchical RR is often used. As shown in Figure 9-5, the ISP provides
Internet routes to AS 100. AS 100 is divided into two clusters, Cluster1 and
Cluster2. Four devices in Cluster1 are core routers and use a backup RR to ensure
reliability.
Flat RR

Figure 9-6 Flat RR

Cluster 4
Cluster 3
Client Client Client Client

Client

Client RR
RR

RR RR Client

Client
Client Client Client
AS100 Cluster 1 Cluster 2

As shown in Figure 9-6, the backbone network is divided into multiple clusters.
RRs of the clusters are non-clients and establish full-mesh connections with each

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other. Although each client only establishes an IBGP connection with its RR, all the
RRs and clients can receive all routing information.

9.2.7 BGP Confederation

In addition to a route reflector, the confederation is another method that reduces
the number of IBGP connections in an AS. A confederation divides an AS into sub-
ASs. Full-mesh IBGP connections are established in each sub-AS. EBGP connections
are established between sub-ASs. ASs outside a confederation still consider the
confederation as an AS. After a confederation divides an AS into sub-ASs, it
assigns a confederation ID (the AS number) to each router within the AS. This
brings two benefits. First, original IBGP attributes are retained, including the
Local_Pref attribute, MED attribute, and Next_Hop attribute. Second,
confederation-related attributes are automatically deleted when being advertised
outside a confederation. Therefore, the administrator does not need to configure
the rules for filtering information such as sub-AS numbers at the egress of a
confederation.

Figure 9-7 Networking diagram of a confederation

EBGP EBGP

IBGP IBGP AS65003

AS65001 AS65002 AS100

As shown in Figure 9-7, AS 100 is divided into three sub-ASs after a confederation
is configured: AS65001, AS65002, and AS65003. The AS number AS 100 is used as
the confederation ID. The number of IBGP connections in AS 100 is then reduced
from 10 to 4, which simplifies the device configuration and reduces the loads on
the network and CPU. In addition, BGP devices outside AS 100 only know the
existence of AS 100 but not the confederation within AS 100. Therefore, the
confederation does not increase the CPU load.

Comparisons Between a Route Reflector and a Confederation

Table 9-3 compares a route reflector and a confederation in terms of the
configuration, device connection, and applications.

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Table 9-3 Comparisons between a route reflector and a confederation

Route Reflector Confederation

Retains the existing network topology Requires the logical topology to be

and ensures compatibility. changed.

Requires only a route reflector to be Requires all devices to be reconfigured.

configured because clients do not need
to know that they are clients of a
route reflector.

Requires full-mesh connections Does not require full-mesh

between clusters. connections between sub-ASs of a
confederation because the sub-ASs are
special EBGP peers.

Applies to medium and large Applies to large networks.

networks.

9.2.8 Route Summarization

The BGP routing table of each device on a large network is large. This burdens
devices, increases the route flapping probability, and affects network stability.

Route summarization is a mechanism that combines multiple routes into one

route. This mechanism allows a BGP device to advertise only the summarized
route but not all the specific routes to peers, therefore reducing the size of the
BGP routing table. If the summarized route flaps, the network is not affected, so
network stability is improved.

BGP supports automatic summarization and manual summarization on IPv4

networks, and supports only manual summarization on IPv6 networks.

● Automatic summarization: summarizes the routes imported by BGP. After

automatic summarization is configured, BGP summarizes routes based on the
natural network segment and advertises only the summarized route to peers.
For example, BGP summarizes 10.1.1.1/24 and 10.2.1.1/24 (two Class A
addresses with non-natural mask) into 10.0.0.0/8 (Class A address with
natural mask).
● Manual summarization: summarizes routes in the local BGP routing table.
Manual summarization can help control the attributes of the summarized
route and determine whether to advertise specific routes.

To prevent routing loops caused by route summarization, BGP uses the AS_Set
attribute. The AS_Set attribute is an unordered set of all ASs that a route passes
through. When the summarized route enters an AS in the AS_Set attribute again,
BGP finds that the local AS number has been recorded in the AS_Set attribute of
the route and discards this route to prevent a routing loop.

9.2.9 Route Dampening

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When BGP is used on complex networks, route flapping occurs frequently. To

prevent frequent route flapping, BGP uses route dampening to suppress unstable
routes.
Route flapping is a process of adding a route to an IP routing table and then
withdrawing this route. When route flapping occurs, a BGP device sends an
Update message to its neighbors. The devices that receive the Update message
need to recalculate routes and modify routing tables. Frequent route flapping
consumes lots of bandwidths and CPU resources and even affects normal network
operation.

Figure 9-8 Diagram of BGP route dampening

Penalty value

suppress value

reuse value
suppress
time
time

half-
life

Route dampening measures the stability of a route using a penalty value. A larger
penalty value indicates a less stable route. As shown in Figure 9-8, each time
route flapping occurs, BGP increases the penalty of this route by a value of 1000.
When the penalty value of a route exceeds the suppression threshold, BGP
suppresses this route, and does not add it to the IP routing table or advertise any
Update message to peers. After a route is suppressed for a period of time (half
life), the penalty value is reduced by half. When the penalty value of a route
decreases to the reuse threshold, the route is reusable and is added to the routing
table. At the same time, BGP advertises an Update message to peers. The
suppression time is the period from when a route is suppressed to when the route
is reusable.
Route dampening applies only to EBGP routes but not IBGP routes. IBGP routes
may include the routes of the local AS, and an IGP network requires that the
routing tables of devices within an AS be the same. If IBGP routes were
dampened, routing tables on devices are inconsistent when these devices have
different dampening parameters. Therefore, route dampening does not apply to
IBGP routes.

9.2.10 BFD for BGP

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BGP periodically sends messages to peers to detect the status of the peers. It takes
more than 1 second for this detection mechanism to detect a fault. When data is
transmitted at gigabit rates, long-time fault detection will cause packet loss. This
cannot meet high reliability requirements of networks. Bidirectional Forwarding
Detection (BFD) provides the millisecond-level fault detection for BGP to improve
network reliability.

Figure 9-9 Networking diagram of BFD for BGP

EBGP
AS100 AS200
RouterA RouterB

As shown in Figure 9-9, RouterA belongs to AS 100 and RouterB belongs to AS

200. RouterA and RouterB are directly connected and establish the EBGP peer
relationship. Association between BGP and BFD is configured on RouterA and
RouterB. When a fault occurs on the link between RouterA and RouterB, BFD can
rapidly detect that the BFD session changes from Up to Down and notify this fault
to RouterA and RouterB. RouterA and RouterB process the neighbor Down event
and select routes again using BGP.

9.2.11 BGP Tracking

BGP tracking provides fast link fault detection to speed up network convergence.
When a fault occurs on the link between BGP peers that have BGP tracking
configured, BGP tracking can quickly detect peer unreachability and instruct the
routing management module to notify BGP of the fault, implementing rapid
network convergence.
Compared to BFD, BGP tracking is easy to configure because it needs to be
configured only on the local device. BGP tracking is a fault detection mechanism
at the routing layer, whereas BFD is a fault detection mechanism at the link layer.
BGP route convergence on a network where BGP tracking is configured is slower
than that on a network where BFD is configured. Therefore, BGP tracking cannot
meet the requirements of voice services that require fast convergence.

Applications
As shown in Figure 9-10, RouterA and RouterB, and RouterB and RouterC
establish IGP connections. RouterA and RouterC establish an IBGP peer
relationship. BGP tracking is configured on RouterA. When a fault occurs on the
link between RouterA and RouterB, IGP performs fast convergence. Subsequently,
BGP tracking detects the unreachability of the route to RouterC and notifies the
fault to BGP on RouterA, which then interrupts the BGP connection with RouterC.

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Figure 9-10 Networking diagram of BGP tracking

RouterA RouterB RouterC

NOTE

If establishing an IBGP peer relationship requires IGP routes, the interval between peer
unreachability discovery and connection interruption needs to be configured, and this
interval must be longer than the IGP route convergence time. Otherwise, the BGP peer
relationship may have been interrupted before IGP route flapping caused by transient
interruption is suppressed, causing unnecessary BGP convergence.

9.2.12 BGP GR and NSR

BGP graceful restart (GR) and non-stop routing (NSR) are high availability
solutions that minimize the impact of device failures on user services.

BGP GR
BGP GR ensures that the forwarding plane continues to guide data forwarding
during a device restart or active/standby switchover. The operations on the control
plane, such as reestablishing peer relationships and performing route calculation,
do not affect the forwarding plane. This mechanism prevents service interruptions
caused by route flapping and improves network reliability.
GR concepts are as follows:
● GR restarter: is the device that is restarted by the administrator or triggered
by failures to perform GR.
● GR helper: is the neighbor that helps the GR restarter to perform GR.
● GR time: is the time during which the GR helper retains forwarding
information after detecting the restart or active/standby switchover of the GR
restarter.
NOTE
In practical application, in order to realize that business forwarding is not affected by
motherboard failure, it is usually possible to configure BGP GR in the hardware
environment of dual motherboard to make sense.
All the models support the GR Helper, and only AR3200 series support the GR Restarter.

BGP GR process is as follows:

1. Using the BGP capability negotiation mechanism, the GR restarter and helper
know each other's GR capability and establish a GR session.
2. When detecting the restart or active/standby switchover of the GR restarter,
the GR helper does not delete the routing information and forwarding entries
of the GR restarter or notify other neighbors of the restart or switchover, but
waits to reestablish a BGP connection with the GR restarter.
3. The GR restarter reestablishes neighbor relationships with all GR helpers
before the GR time expires.

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BGP NSR
NSR is a reliability technique that prevents neighbors from detecting the control
plane switchover. It applies to the devices that have the active and standby MPUs
configured. Compared to GR, NSR does not require the help of neighbors and does
not need to deal with interoperability issues. For details about NSR, see "NSR" in
the Feature Description - Reliability.

NOTE

Only the AR3200 series support NSR.

Comparisons Between Active/Standby Switchovers with and Without GR and

NSR

Table 9-4 Comparisons between active/standby switchovers with and without GR

and NSR
Active/Standby Active/Standby Active/Standby
Switchover Without GR Switchover in GR Mode Switchover in NSR
and NSR Mode

The BGP peer The BGP peer The BGP peer

relationship is relationship is relationship is
reestablished. reestablished. reestablished.

Routes are recalculated. Routes are recalculated. Routes are recalculated.

The forwarding table The forwarding table The forwarding table

changes. remains unchanged. remains unchanged.

Traffic is lost during No traffic is lost during No traffic is lost during

forwarding, and services forwarding, and services forwarding, and services
are interrupted. are not affected. are not affected.

The network detects Except the neighbors of The network does not
route changes, and route the device where the detect route changes.
flapping occurs for a active/standby
short period of time. switchover occurs, other
routers do not detect
route changes.

- The GR restarter requires Neighbors do not need

neighbors to support the to support the NSR
GR helper function. The function.
GR helper function does
not allow multiple
neighbors to perform
active/standby
switchovers in GR mode
simultaneously.

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9.2.13 BGP ORF

The prefix-based BGP outbound route filtering (ORF) capability to advertise
required BGP routes. BGP ORF allows a device to send prefix-based import policies
in a Route-refresh message to BGP peers. BGP peers construct export policies
based on these import policies to filter routes before sending these routes, which
has the following advantages:
● Prevents the local device from receiving a large number of unnecessary
routes.
● Reduces CPU usage of the local device.
● Simplifies the configuration of BGP peers.
● Improves link bandwidth efficiency.

Applications
BGP ORF applies to the scenario when a device wants BGP peers to send only
required routes, and BGP peers do not want to maintain different export policies
for different devices.

Figure 9-11 Inter-AS EBGP peers

AS 100 AS 200

RouterA RouterB

As shown in Figure 9-11, after negotiating the prefix-based ORF capability with
RouterB, RouterA adds the local prefix-based import policies to a Route-refresh
message and sends the message to RouterB. RouterB constructs export policies
based on the received Route-refresh message and sends required routes to
RouterA using a Route-refresh message. RouterA receives only required routes,
and RouterB does not need to maintain routing policies. This reduces the
configuration workload.

Figure 9-12 Intra-AS route reflector

AS 100

RR

RouterA RouterB

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As shown in Figure 9-12, there is a route reflector (RR) in AS 100. RouterA and
RouterB are the clients of the RR. RouterA, RouterB, and the RR negotiate the
prefix-based ORF capability. RouterA and RouterB then add the local prefix-based
import policies to Route-refresh messages and send the messages to the RR. The
RR constructs export policies based on the received import policies and reflects
required routes in Route-refresh messages to RouterA and RouterB. RouterA and
RouterB receive only required routes, and the RR does not need to maintain
routing policies. This reduces the configuration workload.

9.2.14 Dynamic Update Peer-Groups

Currently, the rapid growth in the size of the routing table and the complexity of
the network topology require BGP to support more peers. Especially in the case of
a large number of peers and routes, high-performance grouping and forwarding
are required when a router needs to send routes to a large number of BGP peers,
most of which share the same outbound policies.
The dynamic update peer-groups feature treats all the BGP peers with the same
outbound policies as an update-group. In this case, routes are grouped uniformly
and then sent separately. That is, each route to be sent is grouped once and then
sent to all peers in the update-group, improving grouping efficiency exponentially.
For example, a route reflector (RR) has 100 clients and needs to reflect 100,000
routes to these clients. If the RR sends the routes grouped per peer to 100 clients,
the total number of times that all routes are grouped is 10,000,000 (100,000 x
100). After the dynamic update peer-groups feature is used, the total number of
grouping times changes to 100,000 (100,000 x 1), improving grouping
performance by a factor of 100.

Applications
BGP uses the dynamic update peer-groups technology when a large number of
peers and routes exist and most peers share the same outbound policies,
improving BGP route grouping and forwarding performance. The dynamic update
peer-groups feature applies to the following scenarios:
● International gateway
As shown in Figure 9-13, the Internet gateway (IGW) router sends routes to
all neighboring ASs. If the IGW router supports the dynamic update peer-
groups feature, its BGP route forwarding performance will be greatly
improved.

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Figure 9-13 Networking diagram of the international gateway

AS1000
AS200

AS65001

AS30
Internet Route
IGW
Router

AS100

AS65002

AS120

● RR
As shown in Figure 9-14, RRs send routes to all clients. If the RRs support the
dynamic update peer-groups feature, their BGP route forwarding performance
will be greatly improved.

Figure 9-14 Networking diagram of RRs

AS100

RR1 RR2

IBGP IBGP

Client Client Client Client Client Client

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● ASBR
As shown in Figure 9-15, RouterB, as an Autonomous System Boundary
Router (ASBR), sends all the routes received from an EBGP neighbor RouterA
to all IBGP neighbors. If RouterB supports the dynamic update peer-groups
feature, its BGP route forwarding performance will be greatly improved.

Figure 9-15 Networking diagram of a PE connecting to multiple IBGP

neighbors

AS200
RouterC
IBGP
AS100 RouterD

RouterA
EBGP
RouterB RouterE
IBGP
RouterF

9.2.15 MP-BGP
Traditional BGP-4 manages only IPv4 routing information. Inter-AS transmission of
other network layer protocol packets (such as IPv6 and multicast packets) is
limited. To support multiple network layer protocols, Multiprotocol BGP (MP-BGP)
is designed in RFC 4760 as an extension to BGP-4. MP-BGP uses extended
attributes and address families to support IPv6, multicast, and VPN, without
changing the existing BGP packet forwarding and routing mechanism.

MP-BGP is called BGP4+ on IPv6 unicast networks or called multicast BGP (MBGP)
on IPv4 multicast networks. MP-BGP establishes separate topologies for IPv6
unicast networks and IPv4 multicast networks, and stores IPv6 unicast and IPv4
multicast routing information in different routing tables. This ensures that routing
information of IPv6 unicast networks and IPv4 multicast networks is separated
from each other, and allows routes of different networks to be maintained using
different routing policies.

Extended Attributes
In BGP, an Update message carries three IPv4-related attributes: NLRI, Next_Hop,
and Aggregator.

To support multiple network layer protocols, BGP requires NLRI and Next_Hop
attributes to carry information about network layer protocols. Therefore, MP-BGP
uses the following new optional non-transitive attributes:

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● MP_REACH_NLRI: indicates the multiprotocol reachable NLRI. It is used to

advertise reachable routes and next hop information.
● MP_UNREACH_NLRI: indicates the multiprotocol unreachable NLRI. It is used
to withdraw unreachable routes.

Address Families
MP-BGP uses address families to differentiate network layer protocols. Currently,
devices support the following address family views:
● BGP-IPv4 unicast address family view
● BGP-IPv4 multicast address family view
● BGP-VPN instance IPv4 address family view
● BGP-VPNv4 address family view
● BGP-IPv6 unicast address family view
● BGP-VPN instance IPv6 address family view

9.2.16 BGP 6PE

Background
As IPv6 technology becomes more popular, an increasing number of separate IPv6
networks take shape. IPv6 provider edge (6PE), a technology designed to provide
IPv6 services over IPv4 networks, allows service providers to provide IPv6 services
without constructing IPv6 backbone networks. The 6PE solution connects separate
IPv6 networks using multiprotocol label switching (MPLS) tunnels. The 6PE
solution implements IPv4/IPv6 dual stack on the provider edge devices (PEs) of
Internet service providers and uses the Multi-protocol Extensions for Border
Gateway Protocol (MP-BGP) to assign labels to IPv6 routes. In this manner, the
6PE solution connects separate IPv6 networks over IPv4 tunnels between PEs.

Related Concepts
In practical application, different metropolitan area networks (MANs) of a service
provider or collaborative backbone networks of different service providers often
span multiple autonomous systems (ASs). The 6PE solution can be intra-AS 6PE or
inter-AS 6PE, depending on whether separate IPv6 networks connect to the same
AS. RFC defines three inter-AS 6PE modes: inter-AS 6PE OptionB with autonomous
system boundary routers (ASBRs) as PEs, inter-AS 6PE OptionB, and inter-AS
OptionC. This section describes the following 6PE modes:
● Intra-AS 6PE: Separate IPv6 networks are connected by the same AS. PEs in
the AS exchange IPv6 routes by establishing MP-IBGP peer relationships.
● Inter-AS 6PE OptionB (with ASBRs as PEs): ASBRs in different ASs exchange
IPv6 routes using MP-EBGP.
● Inter-AS 6PE OptionB: ASBRs in different ASs exchange labeled IPv6 routes by
establishing MP-EBGP peer relationships.
● Inter-AS 6PE OptionC: PEs in different ASs exchange labeled IPv6 routes over
multi-hop MP-EBGP peer sessions.

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Intra-AS 6PE
Figure 9-16 shows intra-AS 6PE networking. 6PE runs on the edge of a service
provider network. PEs that connect to IPv6 networks are IPv4/IPv6 dual-stack
devices. PEs and customer edge devices (CEs) exchange IPv6 routes using the IPv6
Interior Gateway Protocol (IGP), or IPv6 External Border Gateway Protocol (EBGP).
PEs exchange IPv4 routes with each other or with provider devices (Ps) using an
IPv4 routing protocol. PEs must establish tunnels to transparently transmit IPv6
packets. PEs often use MPLS label switched paths (LSPs) and MPLS Local IFNET
tunnels. By default, a PE uses an MPLS LSP to transmit IPv6 packets. If no MPLS
LSP is available, a PE uses an MPLS Local IFNET tunnel to transmit IPv6 packets.

Figure 9-16 Intra-AS 6PE networking diagram

MPLS Local Ifnet

or MPLS LSP
IBGP

PE1 P PE2
IPv6 EBGP IPv6 EBGP

CE1 CE2

Figure 9-17 shows route and packet transmission in an intra-AS 6PE scenario. In
this figure, CE2 sends routes to CE1, and CE1 sends packets to CE2. I-L indicates an
inner label, and O-L indicates an outer label. The outer label is allocated by MPLS.
The outer label directs the packet to the BGP next hop, and the inner label
identifies the outbound interface or CE to which the packet should be forwarded.
The route transmission process is as follows:
1. CE2 sends an IPv6 route to PE2, its EBGP peer.
2. Upon receipt, PE2 changes the next hop of the IPv6 route to itself and assigns
a label to the IPv6 route. Then, PE2 sends the labeled IPv6 route to PE1, its
IBGP peer.
3. Upon receipt, PE1 relays the labeled IPv6 route to a tunnel and adds
information about the route to the local forwarding table. Then, PE1 changes
the next hop of the route to itself, removes the label of the route, and sends
the route to CE1, its EBGP peer.
The IPv6 route transmission from CE2 to CE1 is complete.
The packet transmission process is as follows:
1. CE1 sends an ordinary IPv6 packet to PE1 over an IPv6 link on the public
network.
2. Upon receipt, PE1 searches its local forwarding table for the forwarding entry
based on the destination address of the packet and encapsulates the packet

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with inner and outer labels. Then, PE1 sends the IPv6 packet to PE2 over a
public network tunnel.
3. Upon receipt, PE2 removes the inner and outer labels and forwards the IPv6
packet to CE2 over an IPv6 link.
As a result, the IPv6 packet is transmitted from CE1 to CE2.
The route and packet transmission processes show that whether the public
network is an IPv4 or IPv6 network does not matter to the CEs.

Figure 9-17 Route and packet transmission in an intra-AS 6PE scenario

1::1/128 I-L1
1::1/128 NextHop: PE2 1::1/128

CE1 PE1 PE2 CE2

1::1/128
data data data data data data
I-L1 I-L1
Push O-L1 O-L1 Pop

Inter-AS 6PE
● Inter-AS 6PE OptionB (with ASBRs as PEs)
Figure 9-18 shows inter-AS 6PE OptionB (with ASBRs as PEs) networking.
Inter-AS 6PE OptionB (with ASBRs as PEs) is similar to intra-AS 6PE. The only
difference is that in an inter-AS 6PE OptionB scenario in which ASBRs also
function as PEs, ASBRs establish EBGP peer relationships between each other.
The route and packet transmission processes in an inter-AS 6PE OptionB
scenario in which ASBRs also function as PEs are similar to those in an intra-
AS 6PE scenario.

Figure 9-18 Networking diagram for inter-AS 6PE OptionB (with ASBRs as
PEs)

MPLS Local Ifnet

or MPLS LSP

EBGP
ASBR1 ASBR2

IPv6 EBGP IPv6 EBGP

CE1 CE2

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● Inter-AS 6PE OptionB

Figure 9-19 shows inter-AS 6PE OptionB networking. ASBRs exchange labeled
IPv6 routes with each other or with PEs using an IPv4 routing protocol.
Tunnels must be established between ASBRs and between PEs and ASBRs to
transparently transmit IPv6 packets. MPLS LSPs, MPLS Local IFNET tunnels,
MPLS TE tunnels, and GRE tunnels are often used between ASBRs to transmit
IPv6 packets. By default, an ASBR uses an MPLS LSP to transmit IPv6 packets.
If no MPLS LSP is available, an ASBR uses an MPLS Local IFNET tunnel to
transmit IPv6 packets. If you want an ASBR to transmit IPv6 packets over an
MPLS TE or a Generic Routing Encapsulation (GRE) tunnel, configure a tunnel
policy on the ASBR.

Figure 9-19 Networking diagram for inter-AS 6PE OptionB

Tunnel Tunnel Tunnel

IBGP EBGP IBGP

PE1 ASBR1 ASBR2 PE2
IPv6 EBGP

IPv6 EBGP
CE1 CE2

Figure 9-20 shows route and packet transmission in an inter-AS 6PE OptionB
scenario. In this figure, CE2 sends routes to CE1, and CE1 sends packets to
CE2. I-L indicates an inner label, and O-L indicates an outer label.

Figure 9-20 Route and packet transmission in an inter-AS 6PE OptionB

scenario

1::1/128 I-L3 1::1/128 I-L2 1::1/128 I-L1

1::1/128 NextHop: ASBR1 NextHop: ASBR2NextHop: PE2 1::1/128

CE1 PE1 ASBR1 ASBR2 PE2 CE2

1::1/128

data data data data data data data data data data
Push I-L3 I-L3 I-L2 I-L2 I-L1 I-L1
O-L1 O-L1 O-L2 O-L2 O-L3 O-L3 Pop

The route transmission process is as follows:

a. CE2 sends an IPv6 route to PE2, its EBGP peer.
b. Upon receipt, PE2 changes the next hop of the IPv6 route to itself and
assigns a label to the IPv6 route. Then, PE2 sends the labeled IPv6 route
to ASBR2 over an IBGP peer session.

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c. Upon receipt, ASBR2 relays the route to a tunnel and adds information
about the route to the local forwarding table. Then, ASBR2 changes the
next hop of the route to itself, replaces the label of the route, and sends
the route to ASBR1, its EBGP peer.
d. Upon receipt, ASBR1 relays the route to a tunnel and adds information
about the route to the local forwarding table. Then, ASBR1 changes the
next hop of the route to itself, replaces the label of the route, and sends
the route to PE1, its IBGP peer.
e. Upon receipt, PE1 relays the route to a tunnel and adds information
about the route to the local forwarding table. Then, PE1 changes the next
hop of the route to itself, removes the label of the route, and sends the
route to CE1, its EBGP peer.
As a result, the IPv6 route is transmitted from CE2 to CE1.
The packet transmission process is as follows:
a. CE1 sends an ordinary IPv6 packet to PE1 over an IPv6 link on the public
network.
b. Upon receipt, PE1 looks up its local forwarding table based on the
destination address of the packet and encapsulates the packet with inner
and outer labels. Then, PE1 sends the IPv6 packet to ASBR1 over a public
network tunnel.
c. Upon receipt, ASBR1 removes the inner and outer labels of the packet,
looks up the local forwarding table based on the destination address of
the packet, and encapsulates the packet with new inner and outer labels.
Then, ASBR1 sends the IPv6 packet to ASBR2 over a public network
tunnel.
d. Upon receipt, ASBR2 removes the inner and outer labels of the packet,
looks up the local forwarding table based on the destination address of
the packet, and encapsulates the packet with new inner and outer labels.
Then, ASBR2 sends the IPv6 packet to PE2 over a public network LSP.
e. Upon receipt, PE2 removes the inner and outer labels and forwards the
IPv6 packet to CE2 over an IPv6 link.
As a result, the IPv6 packet is transmitted from CE1 to CE2.
● Inter-AS 6PE OptionC
Figure 9-21 shows inter-AS 6PE OptionC networking. In an inter-AS 6PE
OptionC scenario, PEs establish multi-hop MP-EBGP peer relationships
between each other and exchange labeled IPv6 routes using an IPv4 routing
protocol. PEs exchange IPv6 packets over end-to-end BGP LSPs.
NOTE

Two inter-AS 6PE OptionC solutions are available, depending on the establishment
methods of end-to-end LSPs. In an inter-AS 6PE OptionC scenario, PEs establish multi-
hop MP-EBGP peer relationships to exchange labeled IPv6 routes and establish end-to-
end BGP LSPs to transmit IPv6 packets. The way in which an end-to-end BGP LSP is
established does not matter much to inter-AS 6PE OptionC and therefore is not
described here.

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Figure 9-21 Networking diagram for inter-AS 6PE OptionC

Multi-hop MP-EBGP
BGP LSP
MP-IBGP MP-EBGP MP-IBGP
Tunnel Tunnel
Tunnel

PE1 P1 ASBR1 ASBR2 P2 PE2

IPv6 EBGP

IPv6 EBGP
CE1 CE2

Figure 9-22 shows route and packet transmission in an inter-AS 6PE OptionC
scenario. In this figure, CE2 sends routes to CE1, and CE1 sends packets to
CE2. I-L indicates an inner label, B-L indicates a BGP LSP label, and O-L
indicates an outer label.
NOTE

To simplify the description of the figure, it is assumed that:

● The two ASBRs are connected by an MPLS Local IFNET tunnel.
● MPLS does not use the penultimate hop popping (PHP) function.

Figure 9-22 Route and packet transmission in an inter-AS 6PE OptionC

scenario

1::1/128 I-L1
1::1/128 NextHop: PE2 1::1/128

CE1 PE1 P1 ASBR1 ASBR2 P2 PE2 CE2

1::1/128

data data data data data data data data data data data data data data

Push I-L1 I-L1 I-L1 I-L1 I-L1 I-L1 I-L1 I-L1 I-L1 I-L1
B-L1 B-L1 B-L1 B-L1 B-L2 B-L2 O-L3 O-L3 O-L4 O-L4 Pop
O-L1 O-L1 O-L2 O-L2

The route transmission process is as follows:

a. CE2 sends an IPv6 route to PE2, its EBGP peer.
b. Upon receipt, PE2 changes the next hop of the IPv6 route to itself and
assigns a label to the IPv6 route. Then, PE2 sends the labeled IPv6 route
to PE1, its MP-EBGP peer.
c. Upon receipt, PE1 relays the route to a tunnel and adds information
about the route to the local forwarding table. Then, PE1 changes the next
hop of the route to itself, removes the label of the route, and sends the
route to CE1, its EBGP peer.

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The IPv6 route transmission from CE2 to CE1 is complete. During this process,
ASBRs transparently transmit information about the labeled IPv6 route.
The packet transmission process is as follows:
a. CE1 sends an ordinary IPv6 packet to PE1 over an IPv6 link on the public
network.
b. Upon receipt, PE1 searches its local forwarding table for the forwarding
entry based on the destination address of the packet, changes the next
hop of the packet based on the search result, and encapsulates the
packet with an inner label, a BGP LSP label, and an outer label. Then, PE1
sends the IPv6 packet to P1 over a public network tunnel.
c. Upon receipt, P1 replaces the outer label of the packet and forwards the
packet to ASBR1 over a public network tunnel.
d. Upon receipt, ASBR1 removes the outer and BGP LSP labels and
encapsulates the packet with a new BGP LSP label. Then, ASBR1 sends
the IPv6 packet to ASBR2 over a public network tunnel.
e. Upon receipt, ASBR2 removes the BGP LSP label and encapsulates the
packet with an outer label. Then, ASBR2 sends the IPv6 packet to PE2
over a public network tunnel.
f. Upon receipt, P2 replaces the outer label of the packet and forwards the
packet to PE2 over a public network tunnel.
g. Upon receipt, PE2 removes the inner and outer labels and forwards the
IPv6 packet to CE2 over an IPv6 link.
As a result, the IPv6 packet is transmitted from CE1 to CE2.

Usage Scenarios
Each 6PE mode has its advantages and usage scenarios. The intra-AS 6PE mode is
best suited for scenarios in which separate IPv6 networks connect to the same AS.
Inter-AS 6PE modes are best suited for scenarios in which separate IPv6 networks
connect to different ASs. Table 9-5 lists the usage scenarios for inter-AS 6PE
modes.

Table 9-5 Usage scenarios for inter-AS 6PE modes

Mode Characteristic Usage Scenario

Inter-AS 6PE OptionB Advantage: A small network with

(with ASBRs as PEs) Configuration is similar ASBRs in different ASs to
to that for intra-AS 6PE which separate IPv6
and additional inter-AS networks are connected.
configuration is not The smaller the number
required. of ASs spanned, the
Disadvantage: Network more obvious the
expansibility is poor. advantage of this
ASBRs must have high solution is.
performance to manage
information about all
labeled IPv6 routes.

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Mode Characteristic Usage Scenario

Inter-AS 6PE OptionB Advantage: MPLS An inter-AS OptionB

tunnels are established public network with
segment by segment and tunnels established
easy to manage. between the PEs in
Disadvantage: different ASs and with
Information about separate IPv6 networks
labeled IPv6 routes is connected to the ASs.
stored on and advertised
by ASBRs. If a large
number of VPN routes
exist, the overburdened
ASBRs are likely to
encounter bottlenecks.

Inter-AS 6PE OptionC Advantage: An inter-AS OptionC

● Labeled IPv6 routes public network with end-
are directly exchanged to-end tunnels
between the ingress established between the
and egress PEs. PEs in different ASs and
with separate IPv6
● Information about networks connected to
labeled IPv6 routes is the ASs.
managed by PEs only
and ASBRs are no The greater the number
longer the of ASs spanned, the
bottlenecks. more obvious the
advantage of this
Disadvantage: solution is.
Management costs of
end-to-end connections
between PEs are high.

Benefits
6PE offers the following benefits:
● Easy maintenance: All configurations are performed on PEs and network
maintenance is simple. IPv6 services are carried over IPv4 networks, but the
users on IPv6 networks are unaware of IPv4 networks.
● Low network construction costs: Service providers can provide IPv6 services
over existing MPLS networks without upgrading the networks. 6PE devices
can provide multiple types of services, such as IPv6 VPN and IPv4 VPN.

9.2.17 6PE Routes Sharing the Explicit Null Label

On an IPv6 provider edge (6PE) networking, by default, each 6PE route is
assigned. Therefore, each route advertised to other 6PE peers needs to apply for a
label. The number of required labels is directly proportional to the number of 6PE
routes. When there are many 6PE routes, a large number of labels are required.
After 6PE routes sharing the explicit null label is enabled, all 6PE routes share the
explicit null label, without applying for labels. In such a case, the number of

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required labels is irrelevant to the number of 6PE routes, saving label resources on
6PE routers.

The explicit null label is a special label which needs to be popped out on the
egress PE. The packets then must be forwarded on the basis of IPv6.

In the 6PE networking shown in Figure 9-23, 6PE routes sharing the explicit null
label is enabled on 6PE1. 6PE1 then can advertise routes sharing the explicit null
label to 6PE2 without applying for a label for each route. When 6PE2 sends data
to 6PE1, the data packet carries two labels, the top label being the label assigned
by LDP and the bottom label is the explicit null label assigned by MP-BGP. After
the data packet reaches 6PE1, 6PE1 pops the explicit null label and forwards the
IPv6 data packet to CE1.

Figure 9-23 6PE networking diagram

CE1 6PE1 6PE2 CE2

IPv4/MPLS
Backbone

Note that when you enable or disable 6PE routes sharing the explicit null label
after a 6PE peer relationship is set up, temporary packet loss occurs. Therefore,
enable this function prior to setting up a 6PE peer relationship.

9.3 Summary of BGP Configuration Tasks

After basic BGP functions are configured, you can enable basic communication
functions on BGP networks. If other BGP functions are required, configure them
according to reference sections.

Table 9-6 describes the BGP configuration tasks.

NOTE

If BGP is configured on an IPv6 network, all the peer addresses specified in the Peer
command must be IPv6 addresses.

Table 9-6 BGP configuration tasks

Scenario Description Task

Configuring basic BGP The configuration of 9.6 Configuring Basic

functions basic BGP functions is BGP Functions
the foundation of the
BGP network
construction and the
precondition for other
BGP functions.

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Scenario Description Task

Configuring BGP security On BGP networks, 9.7 Configuring BGP

unauthorized users can Security
attack the BGP network
by modifying data
packets or forging
authorized users. To
ensure security of
services carried on BGP
networks, configure BGP
MD5 authentication, BGP
Keychain authentication,
or Generalized TTL
Security Mechanism
(GTSM) function.

Simplifying IBGP Because routes received 9.8 Simplifying IBGP

network connection from the IBGP neighbors Network Connections
will not be sent to other
IBGP neighbors, fully-
meshed connections
must be established on
the IBGP network.
However, when the
number of devices is
large, peer configuration
is very complex on the
fully-meshed IBGP
network, and the
consumption of network
resources and device
CPU resources will
increase. To reduce the
number of IBGP network
connections and better
plan the network,
configure the route
reflector and
confederation.

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Scenario Description Task

Configuring BGP route In a BGP routing table, 9.9 Configuring BGP

selection and load multiple routes to the Route Selection and
balancing same destination may Load Balancing
exist. To guide route
selection, BGP defines
next-hop policies and
route selection rules. The
priority of next-hop
policies is higher than
that of BGP route
selection rules. After the
next-hop policies are
performed, BGP selects
routes according to the
route selection rules.
Usually there are
multiple valid routes to
the same destination on
the network. If BGP only
advertises the optimal
route to its peer,
unbalanced traffic on
different routes will
occur. The BGP load-
balancing configuration
can balance load on
different routes and
reduce network
congestion.

Controlling advertising With the expansion of 9.10 Controlling the

and receiving of BGP the network scale, the Receiving and
routes sharp increase of routing Advertisement of BGP
tables leads to greater Routes
load on networks and
increasing network
security problems. To
solve this problem, filter
routes according to the
routing policies and only
send and receive
required BGP routes. In
addition, multiple routes
to the same destination
may exist. If these routes
need to pass through
different ASs, direct
service traffic to specific
ASs or filter the routes to
be advertised.

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Scenario Description Task

Configuring and To enable BGP to rapidly 9.11 Adjusting the BGP

adjusting the BGP detect network changes, Network Convergence
network convergence speed up the BGP Speed
rate network convergence. To
minimize the effect on
networks from route
flapping and reduce load
on the device, slow down
the BGP network
convergence.

Configuring BGP To avoid long service 9.12 Configuring BGP

reliability interruption when faults Reliability
occur on BGP networks,
adopt the solution of
standby link. However,
the BGP mechanism
requires more than one
second to detect the
faults and perform
active/standby
switchover. To ensure
that users of delay-
sensitive services such as
the voice service do not
detect the service
interruption, associate
BGP tracking, BGP, and
BFD to implement fast
fault detection, and
meanwhile use BGP GR
to perform fast
switchover after the fault
detection.

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Scenario Description Task

Configuring BGP route The BGP routing table on 9.13 Configuring BGP
aggregation a medium or large BGP Route Summarization
network contains a large
number of routing
entries. Storing the
routing table consumes a
large number of memory
resources, and
transmitting and
processing the routing
information consumes a
large number of network
resources. Route
aggregation can reduce
the size of a routing
table, prevent specific
routes from being
advertised, and minimize
the impact of route
flapping on networks.
Although BGP automatic
route aggregation is easy
to configure, it only
aggregates routes
according to the natural
network segment. BGP
manual route
aggregation can be used
with flexible routing
policies to enable BGP to
effectively transmit and
control routes.

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Scenario Description Task

Configuring BGP BGP Outbound Route 9.14 Configuring On-

neighbors to advertise Filters (ORF) is used to demand Route
routes on demand enable BGP neighbors to Advertisement
advertise routes on
demand.
If neighbors of the local
BGP device have
different route
requirements, different
export policies must be
configured on the local
BGP device. In this case,
the configuration
workload and
maintenance costs of the
local BGP device will
increase. To solve this
problem, configure BGP
ORF on BGP neighbor
devices, allowing BGP
neighbor devices to
maintain route policies
on demand and send
them to the local BGP
device as export policies.
This reduces the
configuration workload
and maintenance costs
of the local BGP device.

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Scenario Description Task

Configuring a local BGP The BGP routing table on 9.15 Configuring BGP to
device to send a default a medium or large BGP Advertise Default
route to its peer network contains a large Routes to Peers
number of routing
entries. Storing the
routing table consumes a
large number of memory
resources, and
transmitting and
processing the routing
information consumes a
large number of network
resources. If multiple
routes in a peer BGP
routing table are sent
only from a local device,
configure the local
device to send a default
route to its peer. In this
case, the local device will
send a default route with
the next hop address as
the local address to its
peer, regardless of
whether there is a
default route in the local
routing table. After the
local device is configured
to send only the default
route to its peer using
the routing policies, the
number of network
routes is greatly reduced
and the peer memory
resources and network
resources are largely
saved.

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Scenario Description Task

Configuring path MTU BGP path MTU auto 9.16 Configuring Path
auto discovery discovery allows the MTU Auto Discovery
discovery of the
minimum MTU value
(path MTU) on the
network path from the
source to the
destination, which
enables TCP to transmit
the BGP messages
according to the path
MTU. This increases the
BGP message
transmission efficiency
and improves the BGP
performance.

Configuring MP-BGP Traditional BGP-4 only 9.17 Configuring MP-

manages IPv4 unicast BGP
routing information and
does not support route
transmission between
ASs of other networks
such as IPv6 and
multicast networks. To
support multiple
network layer protocols,
the Internet Engineering
Task Force (IETF)
extends BGP-4 to
Multiprotocol Extensions
for BGP-4 (MP-BGP).
Features supported by
MP-BGP on IPv6
networks are called
BGP4+ and multicast
networks are called
Multicast BGP (MBGP).

9.4 Licensing Requirements and Limitations for BGP

Involved Network Elements
None

Licensing Requirements
BGP is a basic feature of a router and is not under license control.

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Feature Limitations
The QPPB feature is just for beta test, and is not for commercial use. If the feature
is required in the test, contact Huawei technical support personnel.

9.5 Default Settings for BGP

Table 9-7 describes the default settings for BGP.

Table 9-7 Default settings for BGP

Parameter Default Setting

BGP Disabled

Keepalive message interval 60s

Hold time 180s

9.6 Configuring Basic BGP Functions

Before building a BGP network, you need to configure basic BGP functions.

Pre-configuration Tasks
Before configuring basic BGP functions, complete the following task:
● Configuring IP addresses for interfaces to ensure network-layer
communication between neighbor nodes

Configuration Procedure
Perform the following operations in sequence and as required.

9.6.1 Starting a BGP Process

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
BGP is started, the local AS number is specified, and the BGP view is displayed.

NOTICE

After BGP peers are configured, changing the router ID of a BGP peer resets BGP
peer relationships.

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Step 3 Run router-id ipv4-address

NOTE

By default, BGP automatically selects the router ID in the system view. If the IP address of a
physical interface is used as the router ID, route flapping occurs when the IP address of the
physical interface changes. To enhance network stability, configuring the address of a
loopback interface as the router ID is recommended. For Router ID selection rules in the
system view, see descriptions in Command Reference about the router-id command.

----End

9.6.2 Configuring BGP Peers

Context
During the configuration of BGP peers, if the AS number of the specified peer is
the same as the local AS number, an IBGP peer is configured. If the AS number of
the specified peer is different from the local AS number, an EBGP peer is
configured. To enhance the stability of BGP connections, you are advised to use
the reachable loopback interface addresses to establish BGP connections.
When loopback interface addresses are used to establish a BGP connection, run
the peer connect-interface command on both ends of the BGP connection to
ensure the correctness of interfaces and addresses on the TCP connection. If the
command is run on only one end, the BGP connection may fail to be established.
When loopback interface addresses are used to establish an EBGP connection, the
peer ebgp-max-hop command with hop-count greater than or equal to 2 must
be run. Otherwise, the EBGP connection cannot be established.
To perform the same configuration on a large number of peers, configure a BGP
peer group according to 9.6.3 (Optional) Configuring a BGP Peer Group to
reduce the configuration workload.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Run peer { ipv4-address | ipv6-address } as-number { as-number-plain | as-
number-dot }
The BGP peer is created.
By default, BGP does not create BGP peers.
Step 4 (Optional) Run peer ipv4-address connect-interface interface-type interface-
number [ ipv4-source-address ]Or peer ipv6-address connect-interface interface-
type interface-number [ ipv6-source-address ]
A source interface from which BGP packets are sent, and a source address used for
initiating a connection.

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By default, the outbound interface of a BGP packet serves as the source interface
of a BGP packet.

Step 5 (Optional) Run peer connected-check-ignore

The device has been configured not to check the hop count when establishing a
one-hop EBGP peer relationship using a loopback interface address.

NOTE

To allow one-hop EBGP peer relationships to be established using loopback interface

addresses, run the command or the peer ebgp-max-hop command (in which hop-count is
greater than or equal to 2).

Step 6 (Optional) Run peer { ipv4-address | ipv6-address } ebgp-max-hop [ hop-count ]

The maximum number of hops allowed for the establishment of an EBGP

connection is set.

By default, the maximum number of hops allowed for an EBGP connection is 1.

That is, an EBGP connection must be established on a directly connected physical
link.

Step 7 (Optional) Run peer { ipv4-address | ipv6-address } description description-text

The description of the peer is configured.

NOTE

If a BGP peer group is configured on an IPv4 unicast network, steps 7 and 8 are not
required. If a BGP peer group is configured on an IPv4 unicast network and an IPv6 unicast
network, steps 7 and 8 are required.

Step 8 (Optional) Run the following commands as required.

● Run ipv4-family multicast
The BGP-IPv4 multicast address family view is displayed.
● Run ipv6-family [ unicast ]
The BGP-IPv6 unicast address family view is displayed.

Step 9 (Optional) Run peer { ipv4-address | ipv6-address } enable

MP-BGP is enabled on the BGP peers to configure them as MP-BGP peers.

----End

9.6.3 (Optional) Configuring a BGP Peer Group

Context
A large BGP network has a large number of peers. It is difficult to configure and
maintain these peers. You can add the BGP peers with the same configurations to
a BGP peer group and then configure the BGP peers in batches. This simplifies
peer management and improves route advertisement efficiency.

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NOTE

● If a function is configured on a peer and its peer group, the function configured on the peer
takes precedence over that configured on the peer group.
● When loopback interface or sub-interface addresses are used to establish a BGP connection,
you are advised to perform step 6 on both ends of the BGP connection simultaneously to
ensure the correct establishment of the connection. If step 6 is performed on only one end,
the BGP connection may fail to be established.
● When loopback interfaces are used to establish an EBGP connection, step 7 is required and
hop-count in the peer ebgp-max-hop command must be greater than or equal to 2.
Otherwise, the EBGP connection cannot be established.

Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 3 Run group group-name [ external | internal ]

A BGP peer group is created.

NOTE

The AS number of an IBGP peer group is the local AS number. Therefore, step 4 is not
required.

Step 4 Run peer group-name as-number { as-number-plain | as-number-dot }

An AS number is configured for the EBGP peer group.

NOTE

To add an EBGP peer to a peer group, configure the EBGP peer according to 9.6.2
Configuring BGP Peers and then perform step 5.
To add an IBGP peer to a peer group, perform step 5. The system creates an IBGP peer in
the BGP view and sets its AS number as the AS number of the peer group.

Step 5 Run peer { ipv4-address | ipv6-address } group group-name

A peer is added to the peer group.

NOTE

You can repeat step 5 to add multiple peers to a peer group.

Step 6 (Optional) Run peer group-name connect-interface interface-type interface-

number [ ipv4-source-address ]Or peer group-name connect-interface interface-
type interface-number [ ipv6-source-address ]
A source interface and a source IP address are specified for the peer to establish a
TCP connection.

By default, the outbound interface of a BGP packet serves as the source interface
of a BGP packet.

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NOTE

The configurations of GTSM and EBGP-MAX-HOP affect the TTL values of BGP packets,
which may cause a conflict between TTL values. Therefore, you can configure only one of
the two functions for a peer or peer group.

Step 7 (Optional) Run peer group-name ebgp-max-hop [ hop-count ]

The maximum number of hops allowed for the establishment of an EBGP

connection is set.

By default, the maximum number of hops allowed for an EBGP connection is 1.

That is, an EBGP connection must be established on a directly connected physical
link.

Step 8 (Optional) Run peer group-name description description-text

The description is configured for the peer group.

NOTE

If a BGP peer group is configured on an IPv4 unicast network, steps 9 and 10 are not
required. If a BGP peer group is configured on an IPv4 multicast network and an IPv6
unicast network, steps 9 and 10 are required.

Step 9 (Optional) Run the following commands as required.

● Run ipv4-family multicast
The BGP-IPv4 multicast address family view is displayed.
● Run ipv6-family [ unicast ]
The BGP-IPv6 unicast address family view is displayed.

Step 10 Run peer group-name enable

MP-BGP is enabled on the BGP peers to configure them as MP-BGP peers.

----End

9.6.4 Configuring BGP to Import Routes

Context
BGP cannot discover routes and needs to import routes such as IGP routes into
BGP routing tables so that the imported routes can be transmitted within an AS or
between ASs. BGP imports routes in either import or network mode:

● In import mode, BGP imports IGP routes, including RIP, OSPF, and IS-IS routes,
into BGP routing tables based on protocol type. To ensure the validity of
imported IGP routes, BGP can also import static routes and direct routes in
import mode.
● In network mode, BGP imports the routes in the IP routing table one by one
to BGP routing tables. The network mode is more accurate than the import
mode.

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Procedure
● In import mode
a. Run system-view

The system view is displayed.

b. Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

The IPv6 address family view is displayed.
d. Run import-route protocol [ process-id ] [ med med | route-policy
route-policy-name ] *

BGP is configured to import routes of other routing protocols.

e. (Optional) Run default-route imported

BGP is allowed to import default routes from the local IP routing table.

To import default routes, you need to run both the default-route

imported command and the import-route (BGP) command. If only the
import-route (BGP) command is used, default routes cannot be
imported. In addition, the default-route imported command is used to
import only the default routes that exist in the local routing table.

By default, BGP does not add default routes to BGP routing tables.
● In network mode
a. Run system-view

The system view is displayed.

b. Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

The IPv6 address family view is displayed.
d. Run network ipv4-address [ mask | mask-length ] [ route-policy route-
policy-name ]Or network ipv6-address prefix-length [ route-policy
route-policy-name ]

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BGP is configured to import routes from the IPv4 or IPv6 routing table
one by one.
----End

9.6.5 Verifying the Basic BGP Function Configuration

Procedure
● Run the display bgp peer [ verbose ] command to check information about
all BGP peers.
● Run the display bgp peer ipv4-address { log-info | verbose } command to
check information about the specified BGP peer.
● Run the display bgp routing-table [ ipv4-address [ { mask | mask-length }
[ longer-prefixes ] ] ] command to check BGP routing information.
● Run the display bgp group [ group-name ] command to check information
about the specified BGP peer group.
● Run the display bgp multicast peer [ [ peer-address ] verbose ] command to
check information about the specified MBGP peer.
● Run the display bgp multicast group [ group-name ] command to check
information about an MBGP peer group.
● Run the display bgp multicast network command to check the routing
information that MBGP advertises.
● Run the display bgp multicast routing-table [ ip-address [ mask-length
[ longer-prefixes ] | mask [ longer-prefixes ] ] ] command to check the
MBGP routing information of a specified network in the MBGP routing table.
----End

9.7 Configuring BGP Security

Configuring connection authentication and BGP GTSMfor BGP peers can improve
BGP network security.

Pre-configuration Tasks
Before configuring BGP security, complete the following task:
● Configuring Basic BGP Functions

Configuration Procedure
You can perform the following configuration tasks as required. The following
configuration tasks (excluding the task of Verifying the BGP Security
Configuration) can be performed in any sequence.

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9.7.1 Configuring MD5 Authentication

Context
BGP uses TCP as the transmission protocol, and considers a packet valid as long as
the source address, destination address, source port, destination port, and TCP
sequence number of the packet are correct. However, most parameters in a packet
may be easily obtained by attackers. To protect BGP from attacks, MD5
authentication or keychain authentication can be used between BGP peers to
reduce the possibility of attacks. The MD5 algorithm is easy to configure,
generates a single password that needs to be manually changed.

NOTICE

If simple is selected during the configuration of the MD5 authentication

password, the password is saved in the configuration file in plain text. This brings
security risks. It is recommended that you select cipher to save the password in
cipher text. MD5 authentication has potential security risks.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Run peer { ipv4-address | group-name | ipv6-address } password { cipher cipher-
password | simple simple-password }
The MD5 authentication password is set.

NOTE

● To prevent the MD5 password set on BGP peers from being decrypted, update the MD5
password periodically.
● BGP MD5 authentication and BGP keychain authentication are mutually exclusive, and
only one of them can be configured for a BGP peer.

----End

9.7.2 Configuring Keychain Authentication

Context
BGP uses TCP as the transmission protocol, and considers a packet valid as long as
the source address, destination address, source port, destination port, and TCP
sequence number of the packet are correct. However, most parameters in a packet
may be easily obtained by attackers. To protect BGP from attacks, use MD5
authentication or keychain authentication between BGP peers to reduce the

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possibility of attacks. The keychain algorithm is complex to configure and

generates a set of passwords. Keychain authentication allows automatically
changing a password based on the configuration. Therefore, keychain
authentication applies to networks requiring high security.

NOTE

Before configuring BGP keychain authentication, configure a keychain corresponding to

keychain-name. Otherwise, the TCP connection cannot be established. For details about
configuring a keychain, see Keychain Configuration in the Huawei AR Series Configuration
Guide - Security Configuration.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Run peer { ipv4-address | group-name | ipv6-address } keychain keychain-name
Keychain authentication is configured.

NOTE

● You must configure keychain authentication on both BGP peers. Encryption algorithms
and passwords configured on both peers must be the same; otherwise, the TCP
connection cannot be established between BGP peers and BGP messages cannot be
transmitted. SHA256 and HMAC-SHA256 encryption algorithm are recommended in
keychain authentication.
● BGP MD5 authentication and BGP keychain authentication are mutually exclusive, and
only one of them can be configured for a BGP peer.

----End

9.7.3 Configuring BGP GTSM

Context
To protect a device against the attacks of forged BGP packets, you can configure
GTSM to check whether the TTL value in the IP packet header is within the
specified range. GTSM allows or discards packets of which TTL values are not
within the specified range according to networking requirements. When the
default action to be taken on packets is set to drop in GTSM, set a proper TTL
range according to the network topology. Then packets of which TTL values are
not within the specified range are discarded. This prevents attackers from sending
forged BGP packets to consume CPU resources.

Procedure
Step 1 Run system-view
The system view is displayed.

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Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

NOTE

The configurations of GTSM and peer ebgp-max-hop affect the TTL values of BGP packets,
which may cause a conflict between TTL values. Therefore, you can configure only one of
the two functions for a peer or peer group.

Step 3 Run peer { group-name | ipv4-address | ipv6-address } valid-ttl-hops [ hops ]

BGP GTSM is configured.

By default, GTSM is not configured on any BGP peer or peer group.

Step 4 (Optional) Run the following command in the system view:

gtsm default-action { drop | pass }

The default action to be taken on the packets that do not match a GTSM policy is
set.

By default, the action to be taken on the packets that do not match the GTSM
policy is pass.

Step 5 (Optional) Run the following command in the system view:

gtsm log drop-packet all

The log function is enabled on boards.

The log records information that GTSM drops packets, which helps locate faults.

----End

9.7.4 Verifying the BGP Security Configuration

Procedure
● Run the display bgp peer verbose command to check authentication detailed
information about the specified BGP peer.

----End

9.8 Simplifying IBGP Network Connections

Configuring a route reflector and a confederation on an IBGP network can simplify
IBGP network connections.

Pre-configuration Tasks
Before simplifying IBGP network connections, complete the following
configuration task:

● Configuring Basic BGP Functions

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Configuration Procedure
Perform the following configuration tasks in any sequence as required.

9.8.1 Configuring a BGP Route Reflector

Context
To ensure the connectivity between IBGP peers within an AS, you need to establish
full-mesh connections between the IBGP peers. When there are many IBGP peers,
it is costly to establish a fully-meshed network. A route reflector (RR) can solve
this problem.
A cluster ID can help prevent routing loops between multiple RRs within a cluster
and between clusters. When a cluster has multiple RRs, the same cluster ID must
be configured for all the RRs within the cluster.
If full-mesh IBGP connections are established between clients of multiple RRs,
route reflection between clients is not required and wastes bandwidth resources.
In this case, prohibit route reflection between clients to reduce the network
burden.
Within an AS, an RR transmits routing information and forwards traffic. When an
RR connects to a large number of clients and non-clients, many CPU resources are
consumed if the RR transmits routing information and forwards traffic
simultaneously. This also reduces route transmission efficiency. To improve route
transmission efficiency, prohibit BGP from adding preferred routes to IP routing
tables on the RR to enable the RR only to transmit routing information.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
BGP is enabled and the BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family unicast
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.
Step 4 Run peer { group-name | ipv4-address | ipv6-address } reflect-client
An RR and its client are configured.
By default, the route reflector and its client are not configured.
Step 5 (Optional) Run reflector cluster-id cluster-id
A cluster ID is configured for the RR.
By default, each RR uses its router ID as the cluster ID.

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Step 6 (Optional) Run undo reflect between-clients

Route reflection is prohibited between clients.

By default, route reflection is allowed between clients.

Step 7 (Optional) Run routing-table rib-only [ route-policy route-policy-name ]

BGP is prohibited from adding preferred routes to IP routing tables.

By default, BGP adds preferred routes to IP routing tables.

----End

Verifying the Configuration

● Run the display bgp group [ group-name ] command to check information
about the specified BGP peer group.
● Run the display bgp routing-table [ ipv4-address [ { mask | mask-length }
[ longer-prefixes ] ] ] command to check routing information in a BGP
routing table.
● Run the display bgp multicast routing-table [ ip-address [ mask-length
[ longer-prefixes ] | mask [ longer-prefixes ] ] ] command to check the
MBGP routing table.

9.8.2 Configuring a BGP Confederation

Context
A confederation divides an AS into sub-ASs. Within each sub-AS, IBGP peers
establish full-mesh connections or have an RR configured. Sub-ASs establish EBGP
connections. On a large BGP network, configuring a confederation can reduce the
number of IBGP connections, simplify routing policy management, and improve
route advertisement efficiency.

Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bgp { as-number-plain | as-number-dot }

BGP is enabled and the BGP view is displayed.

Step 3 Run confederation id { as-number-plain | as-number-dot }

A confederation ID is configured.

By default, no BGP confederation is configured.

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NOTICE

An old speaker that has a 2-byte AS number cannot be in the same confederation
with a new speaker that has a 4-byte AS number. Otherwise, a routing loop may
occur. This is because the AS4_Path attribute does not support confederations.

Step 4 Run confederation peer-as { as-number-plain | as-number-dot } &<1-32>

A sub-AS number is configured for a confederation.
By default, no sub-AS number of the confederation is configured.
Step 5 (Optional) Run confederation nonstandard
Confederation compatibility is configured.
By default, confederations comply with RFC 3065.
----End

Verifying the Configuration

● Run the display bgp peer [ ipv4-address ] verbose command to check
detailed information about BGP peers.
● Run the display bgp routing-table [ ipv4-address [ { mask | mask-length }
[ longer-prefixes ] ] ] command to check routing information in a BGP
routing table.

9.9 Configuring BGP Route Selection and Load

Balancing
BGP has many route attributes. These attributes can be configured to change the
route selection result.

Pre-configuration Tasks
Before configuring BGP route attributes, complete the following task:
● Configure Basic BGP Functions.

Configuration Procedure
Perform the following configuration tasks as required. The following configuration
tasks (excluding the task of Verifying the BGP Route Selection and Load Balancing
Configuration) can be performed in any sequence. For detailed route selection
rules, see 9.2.5 BGP Route Selection Rules and Load Balancing.

9.9.1 Configuring the BGP Priority

Context
The routing protocols may share and select routing information because routers
may run multiple dynamic routing protocols at the same time. The system sets a

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default priority for each routing protocol. When multiple routing protocols are
used to select routes, the route selected by the routing protocol with a higher
priority takes effect.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.
Step 4 Run preference { external internal local | route-policy route-policy-name } or
preference external internal local route-policy route-policy-name
The BGP priority is set.
The default BGP priority is 255.
The smaller the preference value, the higher the preference.
BGP has the following types of routes:
● EBGP routes learned from peers in other ASs
● IBGP routes learned from peers in the same AS
● Locally originated routes (A locally originated route is a route summarized by
using the summary automatic command or the aggregate command.)
Different preference values can be set for these three types of routes.
In addition, a routing policy can also be used to set the preferences for the routes
that match the policy. The routes that do not match the policy use the default
preference.
If both external internal local and route-policy route-policy-name are specified in
the command, the priority of the routes that match the route-policy is set based
on the route-policy, and the priorities of other routes are set based on the external
internal local configuration.
----End

9.9.2 Configuring the Next_Hop Attribute

Context
When an Autonomous System Boundary Router (ASBR) forwards the route
learned from an EBGP peer to an IBGP peer, the ASBR does not change the next

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hop of the route by default. When the IBGP peer receives this route, it finds the
next hop unreachable, sets the route to inactive, and does not use this route to
guide traffic forwarding. To enable the IBGP peer to use this route to guide traffic
forwarding, configure the ASBR to set its IP address as the next hop of the route
when the ASBR forwards this route to the IBGP peer. After the IBGP peer receives
the route from the ASBR, it finds the next hop of the route reachable, sets the
route to active, and uses this route to guide traffic forwarding.
When a BGP route changes, BGP needs to iterate the indirect next hop of the
route again. If no restriction is imposed on the iterated route, BGP may iterate the
next hop to an incorrect forwarding path, causing traffic loss. To prevent traffic
loss, configure routing policy-based route iteration.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.
Step 4 Perform either of the following operations as required:
● Run peer { ipv4-address | group-name | ipv6-address } next-hop-local
A BGP device is configured to set its IP address as the next hop when the
device advertises routes to an IBGP peer or an IBGP peer group.
By default, a BGP device does not modify the next-hop address when
advertising routes to its IBGP peers.
● Run nexthop recursive-lookup route-policy route-policy-name
Routing-policy-based next hop iteration is configured.
By default, routing-policy-based next hop iteration is not configured.
● Run the following command in the IPv4 unicast address family view:
peer { ipv4-address | group-name } next-hop-invariable
The device is prevented from changing the next-hop address of a route
imported from an IGP before advertising the route to an IBGP peer.
By default, a device changes the next-hop address of a route imported from
an IGP to the address of the interface connecting the device to its peer when
advertising the route to an IBGP peer.
NOTE

The nexthop recursive-lookup route-policy route-policy-name command does not take

effect for the routes received from direct connected EBGP peers.

----End

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9.9.3 Configuring the PrefVal Attribute

Context
The PrefVal attribute is a Huawei proprietary attribute and is valid only on the
device where it is configured. When a BGP routing table contains multiple routes
to the same destination, BGP prefers the route with the highest PrefVal.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.
Step 4 Run peer { group-name | ipv4-address | ipv6-address } preferred-value value
The PrefVal attribute is configured for all the routes learned from a specified peer.
By default, the PrefVal of a route learned from a peer is 0.

----End

9.9.4 Configuring the Default Local_Pref Attribute

Context
The Local_Pref attribute is used to determine the optimal route for outgoing
traffic of an AS. When a BGP device obtains multiple routes to the same
destination address but with different next hops from different IBGP peers, the
BGP device prefers the route with the highest Local_Pref.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.

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● Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.

Step 4 Run default local-preference local-preference

The default Local_Pref attribute is configured.

By default, the Local_Pref attribute is 100.

----End

9.9.5 Configuring the AS_Path Attribute

Context
The AS_Path attribute records all the ASs that a route passes through from the
source to the destination in the vector order. You can configure the AS_Path
attribute to implement flexible route selection.

● Generally, BGP compares the AS_Path lists of routes and prefers the route
with the shortest AS_Path list. When the AS_Path attribute is not required in
route selection, configure BGP not to compare the AS_Path lists of routes
during route selection.
● In most cases, BGP detects routing loops based on AS number. However, to
ensure correct route transmission on a hub-and-spoke network, you need to
configure all the BGP peers that VPN routes advertised from a hub CE to a
spoke CE pass through to accept the routes with a repeated AS number.
● Public AS numbers can be used on the Internet, but private AS numbers
cannot because they may cause routing loops. To prevent routing loops,
configure the AS_Path attribute to carry only public AS numbers in EBGP
Update messages.
● When the AS_Path attribute is reconstructed or summarized routes are
generated, you can set the maximum number of AS numbers in the AS_Path
attribute. Then a BGP device checks whether the number of AS numbers in
the AS_Path attribute of a route exceeds the maximum value. If so, the BGP
device discards the route.
● A device usually supports only one BGP process. This indicates that a device
supports only one AS number. In some cases, for example, when network
migration changes an AS number, you can set a fake AS number to ensure
successful network migration.
● BGP checks the first AS number in the AS_Path list that is carried in the
Update message sent by an EBGP peer. If the first AS number specifies the AS
where the EBGP peer resides, BGP accepts the Update message. Otherwise,
BGP rejects the Update message and interrupts the EBGP connection. If you
do not want BGP to check the first AS number, disable BGP from checking the
first AS number.

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Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run route-policy route-policy-name { deny | permit } node node

A node is configured for a route-policy, and the view of the route-policy is

displayed.

Step 3 (Optional) Configure matching rules for the route-policy to change only the
community attributes of the routes that meet the matching rules.

By default, all routes meet matching rules. For details, see 10.7.2 (Optional)
Configuring an if-match Clause.

Step 4 Run apply as-path { as-number-plain | as-number-dot } &<1-10> { additive |

overwrite }

The AS_Path attribute is set for BGP routes.

Step 5 Run quit

Return to the system view.

Step 6 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 7 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.

Step 8 Add the AS_Path attribute to routes.

● Run peer { ipv4-address | group-name | ipv6-address } route-policy route-
policy-name export
The AS_Path attribute is added to the routes advertised to BGP peers or peer
groups.
● Run peer { ipv4-address | group-name | ipv6-address } route-policy route-
policy-name import
The AS_Path attribute is added to the routes received from BGP peers or peer
groups.
● Run import-route protocol [ process-id ] route-policy route-policy-name
The AS_Path attribute is added to the routes imported by BGP in import
mode.
● Run network { ipv4-address [ mask | mask-length ] | ipv6-address prefix-
length } route-policy route-policy-name
The AS_Path attribute is added to the routes imported by BGP in network
mode.

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Step 9 (Optional) Run one of the following commands to configure the AS_Path attribute
as required.
● Run bestroute as-path-ignore
BGP is configured not to compare the AS_Path attributes of routes during
route selection.
By default, BGP compares the AS_Path attributes of routes during route
selection.
● Run peer { ipv4-address | group-name | ipv6-address } allow-as-loop
[ number ]
Repeated local AS numbers are allowed in routes.
By default, repeated local AS number is not allowed.
● Run peer { ipv4-address | group-name | ipv6-address } public-as-only
BGP is configured to carry only public AS numbers in the AS_Path attribute in
an EBGP Update message.
By default, the AS_Path attribute can carry both public and private AS
numbers in an EBGP Update message.
● Return to the BGP view to configure the AS_Path attribute.
a. Run quit
Return to the BGP view.
b. (Optional) Run one of the following commands to configure the AS_Path
attribute as required.

▪ Run as-path-limit as-path-limit-num

The maximum number of AS numbers in the AS_Path attribute is set.
By default, the maximum number of AS numbers in the AS_Path
attribute is 255.

▪ Run peer { ipv4-address | group-name | ipv6-address } fake-as { as-

number-plain | as-number-dot } [ prepend-global-as ]
A fake AS number is configured for an EBGP peer group.
The peer fake-as command can be used to hide the actual AS
number of a BGP device. EBGP peers in other ASs will use the fake
AS number of this BGP device to set up EBGP peer relationships with
this device.
By default, EBGP peers establish a connection using a real AS
number.

NOTICE

Running the undo check-first-as command increases the probability

of routing loops. Therefore, exercise caution when using this
command.

▪ Run undo check-first-as

BGP is configured not to check the first AS number in the AS_Path
list that is carried in the Update message sent by an EBGP peer.

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By default, BGP checks the first AS number in the AS_Path list that is
carried in the Update message sent by an EBGP peer.
NOTE

When BGP is disabled from checking the first AS number, run the refresh
bgp command in the user view if you want BGP to check the first AS
number of received routes.

----End

9.9.6 Configuring the MED Attribute

Context
The multi-exit discriminator (MED) helps determine the optimal route for
incoming traffic of an AS. It is similar to the metric used in IGP. When a BGP
device obtains multiple routes to the same destination address but with different
next hops from EBGP peers, the BGP device selects the route with the smallest
MED value as the optimal route.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.
Step 4 Perform one of the following operations as required:
● Run default med med
The default MED value is set.
By default, the MED is 0.
● Run bestroute med-none-as-maximum
BGP defines the MED value as the maximum value if a route does not have
the MED attribute.
By default, BGP uses the default MED value when a route does not have the
MED attribute.
● Run compare-different-as-med
BGP is allowed to compare the MED values of routes received from EBGP
peers in any AS.
By default, BGP compares only the MEDs of the routes received from EBGP
peers within the same AS.

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● Run deterministic-med
The deterministic-MED function is enabled.
By default, the BGP deterministic-MED function is disabled.
● Run bestroute med-confederation
The MED values of routes in a confederation are compared.
By default, BGP compares only the MEDs of the routes from the same AS.

----End

9.9.7 Configuring BGP to Ignore the Metric Value of the Next-

Hop IGP Route When Selecting the Optimal Route

Context
On a BGP network, the BGP device always receives multiple routes with the same
prefix but to different paths from neighbors. BGP must select the optimal route to
the specified prefix to guide packet forwarding. By default, BGP compares the
next-hop IGP route metric values of these routes and selects the route with the
smallest metric value as the optimal route. For detailed BGP route selection rules,
see 9.2.5 BGP Route Selection Rules and Load Balancing.

To customize route selection policies, you can run the bestroute igp-metric-
ignore command to configure BGP to ignore the metric value of the next-hop IGP
route when selecting the optimal route.

Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 3 Enter an address family view based on the network type, and configure the BGP
device on the network.
● Run the ipv4-family { unicast | multicast } command to enter the IPv4
address family view.
● Run the ipv6-family [ unicast ] command to enter the IPv6 address family
view.

Step 4 Run bestroute igp-metric-ignore

BGP is configured to ignore the metric value of the next-hop IGP route when
selecting the optimal route.

----End

9.9.8 Configuring the BGP Community Attribute

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Context
The Community attribute is a private BGP route attribute. It is transmitted
between BGP peers and is not restricted within an AS. The Community attribute
allows a group of BGP devices in multiple ASs to share the same routing policies,
which simplifies routing policy applications and facilitates routing policy
management and maintenance. A BGP device can add or change the community
attributes of routes to be advertised.

Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run route-policy route-policy-name { deny | permit } node node

A node is configured for a route-policy, and the view of the route-policy is

displayed.

Step 3 (Optional) Configure matching rules for the route-policy to change only the
community attributes of the routes that meet the matching rules.

By default, all routes meet matching rules. For details, see 10.7.2 (Optional)
Configuring an if-match Clause.

Step 4 Run either of the following commands to configure the Community attribute.
● Run apply community { community-number | aa:nn | internet | no-advertise
| no-export | no-export-subconfed } &<1-32> [ additive ]
Common community attributes are configured for BGP routes.
NOTE
This command allows you to configure a maximum of 32 community attributes.
● Run apply extcommunity { rt { as-number:nn | ipv4-address:nn } } &<1-16>
[ additive ]
An extended community attribute (route-target) is configured.
Extended community attributes are extensions to community attributes in
services. Currently, only the route-target attribute is supported in VPN.

Step 5 Run quit

Return to the system view.

Step 6 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 7 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.

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Step 8 Add the Community attribute to routes.

● Run peer { ipv4-address | group-name | ipv6-address } route-policy route-
policy-name export
The Community attribute is added to the routes advertised to BGP peers or
peer groups.
● Run peer { ipv4-address | group-name | ipv6-address } route-policy route-
policy-name import
The Community attribute is added to the routes received from BGP peers or
peer groups.
● Run import-route protocol [ process-id ] route-policy route-policy-name
The Community attribute is added to the routes imported by BGP in import
mode.
● Run network { ipv4-address [ mask | mask-length ] | ipv6-address prefix-
length } route-policy route-policy-name
The Community attribute is added to the routes imported by BGP in network
mode.
NOTE

Step 9 is required only when the Community attribute needs to be added to the routes
advertised to BGP peers or peer groups.

Step 9 (Optional) Allow BGP to advertise community attributes when BGP adds
community attributes to the routes advertised to BGP peers or peer groups.
● Run peer { ipv4-address | group-name | ipv6-address } advertise-community
BGP is allowed to advertise community attributes to BGP peers or peer
groups.
By default, BGP does not advertise community attributes to any peer or peer
group.
● To advertise an extended community attribute to a specified peer or peer
group, perform the following steps:
a. Run the peer { ipv4-address | group-name | ipv6-address } advertise-ext-
community command to advertise an extended community attribute to a
specified peer or peer group.
b. Run the ext-community-change enable command to enable the device
to change extended community attributes using a routing policy.
By default, BGP peers cannot change extended community attributes
using a route-policy; specifically, BGP peers advertise only the extended
community attributes carried in routes to a specified peer or peer group,
and the peer route-policy command cannot be used to modify the
extended community attributes.

----End

9.9.9 (Optional) Configuring a QPPB Policy

Context
QoS Policy Propagation Through the Border Gateway Protocol (QPPB) allows the
BGP route sender to classify BGP routes by setting BGP route attributes, and

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allows the BGP route receiver to enforce different local QoS policies on the BGP
routes based on the attributes set by the BGP route sender.
The following describes QPPB implementation:
● The BGP route sender sets different BGP route attributes for different BGP
routes before sending the routes to the BGP route receiver. The attributes
include the AS_Path, community, and extended community attributes.
● The BGP route receiver performs the following operations after receiving the
BGP routes:
a. Sets the associated QoS local IDs for the BGP routes that match routing
policies based on the attributes in the BGP routes, including the AS_Path,
community, and extended community attributes.
b. Enforces different traffic behaviors based on the associated QoS local IDs
during packet forwarding.
c. Creates a local QPPB policy to configure the associated QoS policy for the
BGP routes.
d. Applies the local QPPB policy to an interface to implement the policy on
all the packets that match rules.
NOTE

● The device currently allows a QPPB policy to be applied only to the inbound interface of
the destination route.
● Currently, the device supports only the EBGP QPPB policies of the public and private
networks and does not support IBGP QPPB policies.
● QPPB policies support the following traffic behaviors: packet filtering, traffic policing,
remarking, traffic statistics collection, and congestion management.
● Currently, only IPv4 route forwarding supports QPPB policies, and IPv6 route forwarding
does not support QPPB policies.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run qppb local-policy policy-name
A QPPB policy is created.
By default, no QPPB policy is created.
Step 3 Run qos-local-id qos-local-id behavior behavior
The QoS local ID carried in a local route is bound to the specified traffic behavior.
By default, the QoS local ID carried in a local route is not bound to any traffic
behavior.

NOTE
Before running this command, ensure that the following conditions have been met:
● The apply qos-local-idqos-local-id command has been executed in the route-policy
view to configure a QoS local ID for the route requiring QoS control.
● The traffic behavior behavior-name command has been executed in the system view to
create a traffic behavior.

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Step 4 Run quit

Return to the system view.
Step 5 Run interface interface-type interface-number
The interface view is displayed.
Step 6 Run qppb-policy policy-name enable
The QPPB policy has been enabled.
By default, no QPPB policy is enabled.

----End

9.9.10 Configuring BGP Load Balancing

Context
On large networks, there may be multiple valid routes to the same destination.
BGP, however, advertises only the optimal route to its peers. This may result in
unbalanced traffic on different routes. Configuring BGP load balancing enables
traffic to be load balanced and network congestion to be reduced.
Equal-cost BGP routes can only be generated for traffic load balancing when the
first eight route attributes described in "BGP Route Selection Policies" are the
same. Change load balancing rules by adjusting some configurations, for example,
ignoring the comparison of the AS_Path attribute. When adjusting these
configurations, ensure that these configurations do not result in routing loops.
Local cross routes and routes imported between public network and VPN instances
do not support load balancing.

NOTE

If BGP load balancing is configured, the local device changes the next-hop address of routes
to its address when advertising routes to IBGP peer groups, regardless of whether the peer
next-hop-local command is used.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.

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Step 4 Run maximum load-balancing [ ebgp | ibgp ] number [ ecmp-nexthop-

changed ]
The maximum number of BGP routes to be used for load balancing is set.
By default, the maximum number of BGP routes to be used for load balancing is
1, indicating that load balancing is not implemented.

NOTE

● On a public network, if the routes to the same destination implement load balancing,
the system will determine the optimal route type. If the optimal routes are IBGP routes,
only IBGP routes carry out load balancing. If the optimal routes are EBGP routes, only
EBGP routes carry out load balancing. This means that load balancing cannot be
implemented among IBGP and EBGP routes with the same destination address.

NOTICE

Configuring BGP not to compare the AS_Path attributes of the routes to be used
for load balancing may cause routing loops.

Step 5 (Optional) Run load-balancing as-path-ignore

BGP is configured not to compare the AS_Path attributes of the routes to be used
for load balancing.
By default, BGP compares the AS_Path attributes of the routes to be used for load
balancing.

----End

9.9.11 Verifying the BGP Route Selection and Load Balancing

Configuration

Procedure
● Run the display bgp paths [ as-regular-expression ] command to check BGP
AS_Path information.
● Run the display bgp routing-table different-origin-as command to check
the routes with the same destination address but different origin ASs.
● Run the display bgp routing-table regular-expression as-regular-expression
command to check information about routes that match the AS regular
expression.
● Run the display bgp routing-table [ ipv4-address [ { mask | mask-length }
[ longer-prefixes ] ] ] command to check routing information in a BGP
routing table.
● Run the display bgp routing-table community [ community-number |
aa:nn ] &<1-29> [ internet | no-advertise | no-export | no-export-
subconfed ] * [ whole-match ] command to check routing information with
the specified BGP community.
● Run the display bgp routing-table community-filter { { community-filter-
name | basic-community-filter-number } [ whole-match ] | advanced-

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community-filter-number } command to check information about routes

matching a specified BGP community filter.
● Run the display bgp multicast routing-table [ ip-address [ mask-length
[ longer-prefixes ] | mask [ longer-prefixes ] ] ] command to check the
MBGP routing table.
● Run the display bgp multicast routing-table statistics command to check
statistics about the MBGP routing table.

----End

9.10 Controlling the Receiving and Advertisement of

BGP Routes
Controlling the receiving and advertisement of BGP routes can reduce the routing
table size and improve network security.

Pre-configuration Tasks
Before controlling the receiving and advertisement of BGP routes, complete the
following task:

● Configuring Basic BGP Functions

Configuration Procedure

Figure 9-24 Flowchart of controlling the receiving and advertisement of BGP

routes

Configuring a Routing
Policy

Controlling the Controlling the Receiving

Advertisement of BGP Routes of BGP Routes

Configuring BGP Soft

Reset

Required steps

9.10.1 Configuring a Routing Policy

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Context
Before controlling the receiving and advertisement of BGP routes, configure
routing policies or filters of routing policies for route selection. For details, see "10
Routing Policy Configuration" in the Huawei AR Series Access Routers
Configuration Guide - IP Routing.

9.10.2 Controlling the Advertisement of BGP Routes

Context
There are usually a large number of routes in a BGP routing table. Transmitting a
great deal of routing information brings a heavy load to devices. Routes to be
advertised need to be controlled to address this problem. You can configure
devices to advertise only routes that these devices want to advertise or routes that
their peers require. Multiple routes to the same destination may exist and traverse
different ASs. Routes to be advertised need to be filtered in order to direct routes
to specific ASs.

Procedure
● Configure a BGP device to advertise routes to all peers or peer groups.

You can configure a BGP device to filter routes to be advertised.

a. Run system-view

The system view is displayed.

b. Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

The IPv6 address family view is displayed.
d. Perform either of the following operations to configure the BGP device to
advertise routes to all peers or peer groups:

▪ To filter routes based on an ACL, run the filter-policy { acl-number |

acl-name acl-name } export [ protocol [ process-id ] ] or the filter-
policy { acl6-number | acl6-name acl6-name } export [ protocol
[ process-id ] ] command.

▪ To filter routes based on an IP prefix list, run the filter-policy ip-

prefix ip-prefix-name export [ protocol [ process-id ] ] or the filter-
policy ipv6-prefix ipv6-prefix-name export [ protocol [ process-id ] ]
command.

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NOTE

If an ACL has been referenced in the filter-policy command but no VPN instance
is specified in the ACL rule, BGP will filter routes including public and private
network routes in all address families. If a VPN instance is specified in the ACL
rule, only the data traffic from the VPN instance will be filtered, and no route of
this VPN instance will be filtered.
● Configure a BGP device to advertise routes to a specific peer or peer group.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

The IPv6 address family view is displayed.
d. Perform any of the following operations to configure the BGP device to
advertise routes to a specific peer or peer group:

▪ To filter routes based on an ACL, run the peer { group-name | ipv4-

address | ipv6-address } filter-policy { acl-number | acl-name acl-
name | acl6-number | acl6-name acl6-name } export command.
▪ To filter routes based on an IP prefix list, run the peer { ipv4-address
| group-name } ip-prefix ip-prefix-name export or the peer { group-
name | ipv6-address } ipv6-prefix ipv6-prefix-name export
command.

▪ To filter routes based on an AS_Path filter, run the peer { ipv4-

address | group-name | ipv6-address } as-path-filter { as-path-filter-
number | as-path-filter-name } export command.
▪ To filter routes based on a route-policy, run the peer { ipv4-address |
group-name | ipv6-address } route-policy route-policy-name export
command.
NOTE

The routing policy applied in the peer route-policy export command does not
support a specific interface as one matching rule. That is, the routing policy does
not support the if-match interface command.

----End

9.10.3 Controlling the Receiving of BGP Routes

Context
When a BGP device is attacked or network configuration errors occur, the BGP
device will receive a large number of routes from its neighbor. As a result, many

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device resources are consumed. Therefore, the administrator must limit the
resources used by the device based on network planning and device capacity. BGP
provides peer-based route control to limit the number of routes to be sent by a
neighbor. This addresses the preceding problem.

Procedure
● Configure a BGP device to receive routes from all its peers or peer groups.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

The IPv6 address family view is displayed.
d. Perform either of the following operations to configure the BGP device to
filter the routes received from all its peers or peer groups:

▪ To filter routes based on an ACL, run the filter-policy { acl-number |

acl-name acl-name } import or the filter-policy { acl6-number |
acl6-name acl6-name } import command.

▪ To filter routes based on an IP prefix list, run the filter-policy ip-

prefix ip-prefix-name import or the filter-policy ipv6-prefix ipv6-
prefix-name import command.
NOTE

If an ACL has been referenced in the filter-policy command but no VPN instance
is specified in the ACL rule, BGP will filter routes including public and private
network routes in all address families. If a VPN instance is specified in the ACL
rule, only the data traffic from the VPN instance will be filtered, and no route of
this VPN instance will be filtered.
● Configure a BGP device to receive routes from a specific peer or peer group.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

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The IPv6 address family view is displayed.

d. Perform any of the following operations to configure the BGP device to
filter the routes received from a specific peer or peer group:

▪ To filter routes based on an ACL, run the peer { group-name | ipv4-

address | ipv6-address } filter-policy { acl-number | acl-name acl-
name | acl6-number | acl6-name acl6-name } import command.

▪ To filter routes based on an IP prefix list, run the peer { ipv4-address

| group-name } ip-prefix ip-prefix-name import or the peer { group-
name | ipv6-address } ipv6-prefix ipv6-prefix-name import
command.

▪ To filter routes based on an AS_Path filter, run the peer { ipv4-

address | group-name | ipv6-address } as-path-filter { as-path-filter-
number | as-path-filter-name } import command.

▪ To filter routes based on a route-policy, run the peer { ipv4-address |

group-name | ipv6-address } route-policy route-policy-name import
command.
NOTE

The routing policy applied in the peer route-policy import command does not
support a specific interface as one matching rule. That is, the routing policy does
not support the if-match interface command.

NOTICE

If the number of routes received by the local device exceeds the upper
limit and the peer route-limit command is used for the first time, the
local device and its peer reestablish the peer relationship, regardless of
whether alert-only is set.

e. (Optional) Run peer { group-name | ipv4-address } route-limit limit

[ percentage ] [ alert-only | idle-forever | idle-timeout times ]

The maximum number of routes that can be received from the peer or
peer group is set.

----End

9.10.4 Configuring BGP Soft Reset

Context
After changing a BGP import policy, you must reset BGP connections for the new
import policy to take effect. This, however, interrupts these BGP connections
temporarily. BGP route-refresh allows the system to softly reset BGP connections
to refresh a BGP routing table without tearing down any BGP connection. If a
device's peer does not support route-refresh, configure the device to remain all
routing updates received from the peer so that the device can refresh its routing
table without tearing down the BGP connection with the peer.

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Procedure
● If a device's peer supports route-refresh, configure the device to softly reset
the BGP connection with the peer and update the BGP routing table.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. (Optional) Run peer { ipv4-address | group-name } capability-advertise
route-refreshpeer ipv6-address capability-advertise { 4-byte-as | route-
refresh }or run:
Route-refresh is enabled.
By default, route-refresh is enabled.
d. Run quit
Return to the system view.
e. Run quit
Return to the user view.
f. Run refresh bgp [ vpn-instance vpn-instance-name ipv4-family |
vpnv4 ] { all | ipv4-address | group group-name | external | internal }
{ export | import }
or refresh bgp ipv6 { all | group group-name | ipv6-address | external |
internal } { export | import }
BGP soft reset is configured.
● If a device's peer does not support route-refresh, configure the device to
remain all routing updates received from the peer so that the device can
refresh its routing table without tearing down the BGP connection with the
peer.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

The IPv6 address family view is displayed.

NOTICE

If the peer keep-all-routes command is used on the device for the first
time, the sessions between the device and its peers are reestablished.
The refresh bgp command takes effect when the peer keep-all-routes
command is used on the device supporting route-refresh.

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d. Run peer { ipv4-address | group-name | ipv6-address } keep-all-routes

The device is configured to store all the routing updates received from its
peers or peer groups.
By default, the device stores only the routing updates that are received
from peers or peer groups and match a configured import policy.
----End

9.10.5 Verifying the BGP Route Receiving and Advertisement

Control Configuration

Procedure
● Run the display ip as-path-filter [ as-path-filter-number | as-path-filter-
name ] command to check information about a configured AS_Path filter.
● Run the display ip community-filter [ basic-comm-filter-num | adv-comm-
filter-num | comm-filter-name ] command to check information about a
configured community filter.
● Run the display ip extcommunity-filter [ basic-extcomm-filter-num |
advanced-extcomm-filter-num | extcomm-filter-name ] command to check
information about a configured extcommunity filter.
● Run the display bgp routing-table as-path-filter { as-path-filter-number |
as-path-filter-name } command to check information about routes matching
a specified AS_Path filter.
● Run the display bgp routing-table community-filter { { community-filter-
name | basic-community-filter-number } [ whole-match ] | advanced-
community-filter-number } command to check information about routes
matching a specified BGP community filter.
● Run the display bgp routing-table peer ipv4-address received-routes
[ active ] [ statistics ] command to check information about routes received
by a BGP device from its peers.
● Run the display bgp multicast routing-table different-origin-as command
to check information about MBGP routes with different origin ASs.
● Run the display bgp multicast routing-table regular-expression as-regular-
expression to check information about MBGP routes matching the AS regular
expression.
● Run the display bgp multicast paths [ as-regular-expression ] command to
check information about AS paths.
● Run the display bgp multicast routing-table as-path-filter { as-path-filter-
number | as-path-filter-name } command to check information about MBGP
routes matching the AS_Path filter.
● Run the display bgp multicast routing-table community-filter
{ { community-filter-name | basic-community-filter-number } [ whole-
match ] | advanced-community-filter-number } command to check
information about routes matching a specified MBGP community filter.
● Run the display bgp multicast routing-table peer peer-address
{ advertised-routes [ network [ { mask | mask-length } [ longer-
prefixes ] ] ] | received-routes [ active ] | accepted-routes } command to

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check information about routes that are sent by and received from the
specified MBGP peer.
● Run the display bgp multicast network command to check the routing
information that MBGP advertises.
----End

9.11 Adjusting the BGP Network Convergence Speed

You can configure BGP timers, disable rapid EBGP connection reset, and configure
BGP route dampening to speed up BGP network convergence and improve BGP
security.

Pre-configuration Tasks
Before configuring adjusting the BGP network convergence speed, complete the
following task:
● Configuring Basic BGP Functions

Configuration Procedure
You can perform the following configuration tasks as required. The following
configuration tasks (excluding the task of Verifying the BGP Network Convergence
Speed Adjustment Configuration) can be performed in any sequence.

9.11.1 Configuring a BGP ConnectRetry Timer

Context
After BGP initiates a TCP connection, the ConnectRetry timer will be stopped if the
TCP connection is established successfully. If the first attempt to establish a TCP
connection fails, BGP tries again to establish the TCP connection after the
ConnectRetry timer expires.
● Setting a short ConnectRetry interval reduces the period BGP waits between
attempts to establish a TCP connection. This speeds up the establishment of
the TCP connection.
● Setting a long ConnectRetry interval suppresses routing flapping caused by
peer relationship flapping.
A ConnectRetry timer can be configured either for all peers or peer groups, or for
a specific peer or peer group. A ConnectRetry timer configured for a specific peer
takes precedence over that configured for the peer group of this peer. In addition,
a ConnectRetry timer configured for a specific peer or peer group takes
precedence over that configured for all peers or peer groups.

Procedure
● Configure a BGP ConnectRetry timer for all peers or peer groups.
a. Run system-view
The system view is displayed.

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b. Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.
c. Run timer connect-retry connect-retry-time
A BGP ConnectRetry timer is configured for all peers or peer groups.
By default, the ConnectRetry timer value is 32s.
● Configure a ConnectRetry timer for a specific peer or peer group.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Run peer { group-name | ipv4-address | ipv6-address } timer connect-
retry connect-retry-time
A ConnectRetry timer is configured for a specific peer or peer group.
By default, the ConnectRetry timer value is 32s.
----End

9.11.2 Configuring BGP Keepalive and Hold Timers

Context
Keepalive messages are used by BGP to maintain peer relationships.
● If short Keepalive time and holdtime are set, BGP can detect a link fault
quickly. This speeds up BGP network convergence, but increases the number
of Keepalive messages on the network and loads of devices, and consumes
more network bandwidth resources.
● If long Keepalive time and holdtime are set, the number of Keepalive
messages on the network is reduced, loads of devices are reduced, and fewer
network bandwidths are consumed. If the Keepalive time is too long, BGP is
unable to detect link status changes in a timely manner. This is unhelpful for
implementing rapid BGP network convergence and may cause many packets
to be lost.
Keepalive and hold timers can be configured either for all peers or peer groups, or
for a specific peer or peer group. Keepalive and hold timers configured for a
specific peer take precedence over those configured for the peer group of this
peer. In addition, Keepalive and hold timers configured for a specific peer or peer
group take precedence over those configured for all peers or peer groups.

NOTICE

Changing timer values using the timer command or the peer timer command
interrupts BGP peer relationships between routers.
Setting the Keepalive time to 20s is recommended. If the Keepalive time is smaller
than 20s, sessions between peers may be closed.

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Procedure
● Configure BGP timers for all peers or peer groups.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Run timer keepalive keepalive-time hold hold-time [ min-holdtime
min-holdtime ]
BGP timers are configured.
The proper maximum interval at which Keepalive messages are sent is
one third the holdtime. By default, the Keepalive time is 60s and the
holdtime is 180s.
● Configure BGP timers for a specific peer or peer group.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Run peer { ipv4-address | group-name | ipv6-address } timer keepalive
keepalive-time hold hold-time [ min-holdtime min-holdtime ]
The Keepalive and hold timers are configured for a specific peer or peer
group.
The proper maximum interval at which Keepalive messages are sent is
one third the holdtime. By default, the Keepalive time is 60s and the
holdtime is 180s.
----End

9.11.3 Configuring an Update Message Timer

Context
BGP does not periodically update a routing table. When BGP routes change, BGP
updates the changed BGP routes in the BGP routing table by sending Update
messages.
● If a short Update message interval is set, BGP can fast detect route changes.
This speeds up BGP network convergence, but increases the number of
Update messages on the network and loads of devices, and consumes more
network bandwidth resources.
● If a long Update message interval is set, the number of Update messages on
the network is reduced, loads of devices are reduced, and fewer network
bandwidths are consumed. This avoids network flapping. If the Update
message interval is too long, BGP is unable to detect route changes in a
timely manner. This is unhelpful for implementing rapid BGP network
convergence and may cause many packets to be lost.

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Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.

Step 4 Run peer { ipv4-address | group-name | ipv6-address } route-update-interval

interval
An Update message timer is configured.

By default, the interval at which Update messages are sent to IBGP peers is 15s,
and the interval at which Update messages are sent to EBGP peers is 30s.

Step 5 (Optional) Configure a delay in sending Update messages.

● Run peer { ipv4-address | group-name | ipv6-address } out-delay delay-value
A delay in sending Update messages is set.
The default delay is 0, indicating that Update packets are sent without a
delay.
● Run out-delay delay-value
A global delay in sending Update messages is set.
The default delay value is 0, indicating that the intermediate device on the
primary path sends Update packets without a delay.

----End

9.11.4 Disabling Rapid EBGP Connection Reset

Context
Rapid EBGP connection reset is enabled by default. This allows BGP to
immediately respond to a fault on an interface and delete the direct EBGP sessions
on the interface without waiting for the hold timer to expire and implements rapid
BGP network convergence.

If the status of an interface used to establish an EBGP connection changes

frequently, the EBGP session will be deleted and reestablished repeatedly, causing
network flapping. Rapid EBGP connection reset can be disabled in such a situation.
BGP will delete direct EBGP sessions on the interface until the hold timer expires.
This suppresses BGP network flapping, helps implement rapid BGP network
convergence, and reduces network bandwidth consumption.

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Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 3 Run undo ebgp-interface-sensitive

Rapid EBGP connection reset is disabled.

By default, rapid EBGP connection reset is enabled.

NOTE

Rapid EBGP connection reset enables BGP to quickly respond to interface faults but does
not enable BGP to quickly respond to interface recovery. After the interface recovers, BGP
uses its state machine to restore relevant sessions.
Rapid EBGP connection reset is disabled in a situation where the status of an interface used
to establish an EBGP connection changes frequently. If the status of the interface becomes
stable, run the ebgp-interface-sensitive command to enable rapid EBGP connection reset
to implement rapid BGP network convergence.

----End

9.11.5 Configuring the BGP Next Hop Delayed Response

Context
Configuring the BGP next hop delayed response can speed up BGP route
convergence and minimize traffic loss.

As shown in Figure 9-25, PE1, PE2, and PE3 are the clients of the RR. CE2 is dual-
homed to PE1 and PE2. PE1 and PE2 advertise their routes to CE2 to the RR. The
RR advertises the route from PE1 to PE3. PE3 has a route to CE2 only and
advertises this route to CE1. After the route exchange, CE1 and CE2 can
communicate. If PE1 fails, PE3 detects that the next hop is unreachable and
instructs CE1 to delete the route to CE2. Traffic is interrupted. After BGP route
convergence is complete, the RR selects the route advertised by PE2 and sends a
route update message to PE3. PE3 then advertises this route to CE1, and traffic
forwarding is restored to the normal state. A high volume of traffic will be lost
during traffic interruption because BGP route convergence is rather slow.

If the BGP next hop delayed response is enabled on PE3, PE3 does not reselect a
route or instruct CE1 to delete the route to CE2 immediately after detecting that
the route to PE1 is unreachable. After BGP convergence is complete, the RR selects
the route advertised by PE2 and sends the route to PE3. PE3 then reselects a route
and sends a route update message to CE1. Traffic forwarding is restored to the
normal state. After the BGP next hop delayed response is enabled on PE3, PE3
does not need to delete the route or instruct CE1 to delete the route. This delayed
response speeds up BGP route convergence and minimizes traffic loss.

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Figure 9-25 Networking diagram for configuring the BGP next hop delayed
response

CE1 PE3 P PE1

CE2

RR PE2

The BGP next hop delayed response applies to a scenario where the next hop has
multiple links to reach the same destination. If there is only one link between the
next hop and the destination, configuring the BGP next hop delayed response may
cause heavier traffic loss when the link fails because link switching is impossible.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Run nexthop recursive-lookup delay [ delay-time ]
A delay in responding to a next hop change is set.
By default, the delay in responding to changes of the next hop is not configured.
NOTE

BGP route convergence depends on IGP route convergence. If IGP route convergence is
quick, the default delay time does not need to be changed. If IGP route convergence is slow,
setting a delay time longer than IGP route convergence time is recommended.

----End

9.11.6 Configuring BGP Route Dampening

Context
A route is considered to be flapping when it repeatedly appears and then
disappears in the routing table. BGP generally applies to complex networks where
routes change frequently. Frequent route flapping consumes lots of bandwidths

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and CPU resources and even affects normal network operation. BGP route
dampening prevents frequent route flapping.
BGP can differentiate routes based on policies and use different route dampening
parameters to suppress different routes. For example, on a network, you can set a
long suppression time for routes with a long mask and set a short suppression
time for routes with a short mask (such as 8-bit mask).

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family { unicast | multicast | vpnv4 [ unicast ] | vpn-instance vpn-
instance-name }
The IPv4 address family view is displayed.
● Run ipv6-family [ unicast | vpn-instance vpn-instance-name ]
The IPv6 address family view is displayed.
Step 4 Run dampening [ ibgp ] [ half-life-reach reuse suppress ceiling | route-policy
route-policy-name ] *
BGP route dampening parameters are configured.

NOTE

The dampening command is valid only for EBGP routes.

The dampening ibgp command is valid only for BGP VPNv4 routes.

----End

9.11.7 Verifying the BGP Network Convergence Speed

Adjustment Configuration

Procedure
● Run the display bgp peer [ verbose ] command to check information about
all BGP peers.
● Run the display bgp group [ group-name ] command to check information
about the specified BGP peer group.
● Run the display bgp routing-table dampened command to check dampened
BGP routes.
● Run the display bgp routing-table dampening parameter command to
check configured BGP route dampening parameters.
● Run the display bgp routing-table flap-info [ regular-expression as-
regular-expression | as-path-filter as-path-filter-number | network-address

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[ { mask | mask-length } [ longer-match ] ] ] command to check route

flapping statistics.
● Run the display bgp multicast routing-table dampened command to check
dampened MBGP routes.
● Run the display bgp multicast routing-table dampening parameter
command to check MBGP route dampening parameters.
● Run the following commands to check statistics about flapping MBGP routes.
– display bgp multicast routing-table flap-info [ ip-address [ mask
[ longer-match ] | mask-length [ longer-match ] ] | as-path-filter { as-
path-filter-number | as-path-filter-name }]
– display bgp multicast routing-table flap-info regular-expression as-
regular-expression
----End

9.12 Configuring BGP Reliability

You can configure BGP Tracking, association between BGP and BFD, and BGP GR
to speed up BGP network convergence and improve BGP reliability.

Pre-configuration Tasks
Before configuring BGP reliability, complete the following task:

● Configuring Basic BGP Functions

Configuration Procedure
You can perform the following configuration tasks as required. The following
configuration tasks can be performed in any sequence.

9.12.1 Enabling BGP Tracking

Context
BFD can be configured to detect peer relationship status changes in order to
implement rapid BGP convergence. BFD, however, needs to be configured on the
entire network, and has poor extensibility. If BFD cannot be deployed on a device
to detect BGP peer relationship status, BGP peer tracking can be enabled on the
device to quickly detect link or peer unreachability, implementing rapid network
convergence.

BGP tracking can be used to adjust the interval between peer unreachability
discovery and connection interruption. This suppresses BGP peer relationship
flapping caused by route flapping and improves BGP network stability.

Procedure
Step 1 Run system-view

The system view is displayed.

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Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 3 Run peer { group-name | ipv4-address | ipv6-address } tracking [ delay delay-

time ]
BGP peer tracking is enabled on the device to detect the status of a specified peer.

By default, BGP peer tracking is disabled.

----End

9.12.2 Configuring BFD for BGP

Context
BGP periodically sends Keepalive messages to its peers to detect the status of its
peers. It takes more than 1 second for this detection mechanism to detect a fault.
When data is transmitted at gigabit rates, long-time fault detection will cause
packet loss. This cannot meet high reliability requirements of carrier-class
networks. Association between BGP and BFD can solve this problem. BFD is a
millisecond-level fault detection mechanism. It can detect faults on the link
between BGP peers within 50 ms. Therefore, BFD can speed up BGP route
convergence, ensures fast link switching, and reduces traffic loss.

When a peer joins a peer group on which BFD is enabled, BFD also takes effect on
the peer and a BFD session is created on the peer. To prevent BFD from taking
effect on the peer, run the peer bfd block command.

By default, Huawei devices establish multi-hop IBGP sessions with each other.
When a Huawei device communicates with a non-Huawei device that establishes
a single-hop IBGP session by default, you are advised to configure only association
between IGP and BFD or association between IBGP and BFD.

NOTE
BFD for routing protocols can only be configured on GRE tunnel interfaces.

Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bfd

Global BFD is enabled on the local device.

Step 3 Run quit

Return to the system view.

Step 4 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 5 (Optional) The BGP-VPN instance address family view is displayed.

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● Run ipv4-family vpn-instance vpn-instance-name

The BGP-VPN instance IPv4 address family view is displayed.
● Run ipv6-family vpn-instance vpn-instance-name
The BGP-VPN instance IPv6 address family view is displayed.

NOTE

BFD for BGP can be configured for the VPN in this view. To configure BFD for BGP for the
public network, skip this step.

Step 6 Run peer { group-name | ipv4-address | ipv6-address } bfd enable [ single-hop-

prefer ]
BFD is configured for the peer or peer group, and default BFD parameters are
used to establish BFD sessions.
If BFD is configured for a peer group, BFD sessions are created for the peers on
which the peer bfd block command is not used.
Step 7 Run peer { group-name | ipv4-address | ipv6-address } bfd { min-tx-interval min-
tx-interval | min-rx-interval min-rx-interval | detect-multiplier multiplier | wtr
wtr-value } *
BFD session parameters are configured.
Step 8 (Optional) Run peer { ipv4-address | ipv6-address } bfd block
The peer is disabled from inheriting the BFD function of the peer group to which
the peer belongs.

NOTE

● BFD sessions are established when they are in Established state.

● If BFD parameters are configured on a peer, BFD sessions are established using these
parameters.
● The peer { ipv4-address | ipv6-address } bfd block and peer { ipv4-address | ipv6-
address } bfd enable commands are mutually exclusive.

----End

Verifying the Configuration

● Run the display bgp bfd session { [ vpnv4 vpn-instance vpn-instance-
name ] peer ipv4-address | all } command to check information about the
BFD sessions established between BGP peers.
● Run the display bgp [ vpnv4 vpn-instance vpn-instance-name ] peer
[ [ ipv4-address ] verbose ] command to check information about BGP peers.
● Run the display bgp group [ group-name ] command to check information
about the specified BGP peer group.
● Run the display bgp vpnv4 { all | vpn-instance vpn-instance-name } group
[ group-name ] command to check information about the BGP VPNv4 peer
group.
● Run the display bgp ipv6 bfd session { [ vpnv6 vpn-instance vpn-instance-
name ] peer ipv6-address | all } command to check information about the
BFD sessions established between BGP peers.

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9.12.3 Configuring the BGP GR Function

Context
BGP restart causes peer relationships reestablishment and traffic interruption.
Graceful restart (GR) ensures uninterrupted traffic forwarding in the case of BGP
restart.

NOTE
In practical application, in order to realize that business forwarding is not affected by
motherboard failure, it is usually possible to configure BGP GR in the hardware
environment of dual motherboard to make sense.
All the models support the GR Helper, and only AR3200 series support the GR Restarter.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Run graceful-restart
BGP GR is enabled.
By default, BGP GR is disabled.
Step 4 (Optional) Run graceful-restart timer wait-for-rib timer
The time during which the restarting speaker and receiving speaker wait for End-
of-RIB messages is set.
By default, the time for waiting for End-of-RIB messages is 600 seconds.
Step 5 (Optional) Run graceful-restart peer-reset
The device is enabled to reset a BGP session in GR mode.
By default, a device is not enabled to reset a BGP connection in GR mode.

----End

Verifying the Configuration

● Run the display bgp peer verbose command to check detailed information
about BGP GR.

9.13 Configuring BGP Route Summarization

On IPv4 networks, BGP supports automatic route summarization and manual
route summarization. Manual route summarization takes precedence over
automatic route summarization. On IPv6 networks, BGP supports only manual
route summarization.

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Pre-configuration Tasks
Before configuring BGP route summarization, complete the following task:
● Configuring Basic BGP Functions

Procedure
● Configure automatic route summarization.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Run ipv4-family { unicast | multicast }
The IPv4 address family view is displayed.
d. Run summary automatic
BGP summarizes subnet routes based on natural mask.

NOTE

The command summarizes the routes imported by BGP. These routes can be direct
routes, static routes, RIP routes, OSPF routes, or IS-IS routes. The command, however,
is invalid for the routes imported using the network command.
● Configure manual route summarization.
a. Run system-view
The system view is displayed.
b. Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
c. Enter the corresponding address family view based on network type to
configure BGP devices on networks.

▪ Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.

▪ Run ipv6-family [ unicast ]

The IPv6 address family view is displayed.
d. Perform any of the following operations to configure manual route
summarization.

▪ To advertise the summarized routes and specific routes, run the

aggregate ipv4-address { mask | mask-length } or the aggregate
ipv6-address prefix-length command.
▪ To advertise only the summarized routes, run the aggregate ipv4-
address { mask | mask-length } detail-suppressed or the aggregate
ipv6-address prefix-length detail-suppressed command.
▪ To advertise the summarized routes and specific routes that meet the
specified route-policy, run the aggregate ipv4-address { mask |

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mask-length } suppress-policy route-policy-name or the aggregate

ipv6-address prefix-length suppress-policy route-policy-name
command.

▪ To advertise the summarized routes of which the AS_Set attribute

helps detect routing loops, run the aggregate ipv4-address { mask |
mask-length } as-set or the aggregate ipv6-address prefix-length as-
set command.

▪ To set attributes for the summarized routes, run the aggregate ipv4-
address { mask | mask-length } attribute-policy route-policy-name
or the aggregate ipv6-address prefix-length attribute-policy route-
policy-name command.
▪ To summarize the specific routes that meet the specified route-policy,
run the aggregate ipv4-address { mask | mask-length } origin-policy
route-policy-name or the aggregate ipv6-address prefix-length
origin-policy route-policy-name command.
NOTE

Manual route summarization is valid for the routes in the local BGP routing table. For
example, if the local BGP routing table does not contain routes with mask longer than
16 bits, such as 10.1.1.1/24, BGP will not generate an aggregated route for it even if
the aggregate 10.1.1.1 16 command is used.

----End

Verifying the Configuration

● Run the display bgp routing-table [ ipv4-address [ { mask | mask-length }
[ longer-prefixes ] ] ] command to check information about summarized
routes.
● Run the display bgp multicast routing-table [ ip-address [ mask-length
[ longer-prefixes ] | mask [ longer-prefixes ] ] ] command to check the
MBGP routing table.

9.14 Configuring On-demand Route Advertisement

If a BGP device only wants to received required routes but its peer cannot
maintain different export policies for connected devices, you can configure prefix-
based BGP outbound route filtering (ORF) to meet this requirement.

Pre-configuration Tasks
Before configuring prefix-based BGP ORF, complete the following tasks:
● Configuring Basic BGP Functions
● Configuring an IP Prefix List

Procedure
Step 1 Run system-view
The system view is displayed.

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Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.
Step 3 Run ipv4-family unicast
The IPv4 unicast address family view is displayed.
Step 4 Run peer { group-name | ipv4-address } ip-prefix ip-prefix-name import
A prefix-based import policy is configured for a peer or peer group.
Step 5 Run peer { group-name | ipv4-address } capability-advertise orf [ non-standard-
compatible ] ip-prefix { both | receive | send }
Prefix-based ORF is enabled for a peer or peer group.
By default, prefix-based ORF is disabled for a peer or peer group.

----End

Verifying the Configuration

● Run the display bgp peer [ ipv4-address ] verbose command to check
detailed information about BGP peers.
● Run the display bgp peer ipv4-address orf ip-prefix command to check
prefix-based BGP ORF information received from a specified peer.

9.15 Configuring BGP to Advertise Default Routes to

Peers
If a BGP device needs to send multiple routes to its peer, the BGP device can be
configured to send only a default route with the local address as the next-hop
address to its peer, regardless of whether there are default routes in the local
routing table. This function reduces the number of network routes and saves
memory and network resources.

Pre-configuration Tasks
Before configuring BGP to send default routes to peers, complete the following
task:
● Configuring Basic BGP Functions

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.

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● Run ipv4-family { unicast | multicast }

The IPv4 address family view is displayed.
● Run ipv6-family [ unicast ]
The IPv6 address family view is displayed.

Step 4 Run peer { group-name | ipv4-address | ipv6-address } default-route-advertise

[ route-policy route-policy-name ] [ conditional-route-match-all { ipv4-address1
{ mask1 | mask-length1 } } &<1-4> | conditional-route-match-any { ipv4-
address2 { mask2 | mask-length2 } } &<1-4> ]
A BGP device is configured to send default routes to a peer or peer group.

NOTE

The conditional-route-match-all and conditional-route-match-any keywords are not

supported in the IPv4 multicast address family view and the IPv6 address family view.

----End

Verifying the Configuration

● Run the display bgp routing-table [ ipv4-address [ mask | mask-length
[ longer-prefixes ] ] ] command to check received BGP default routes.
● Run the display bgp multicast routing-table [ ip-address [ mask-length
[ longer-prefixes ] | mask [ longer-prefixes ] ] ] command to check received
MBGP default routes.

9.16 Configuring Path MTU Auto Discovery

BGP path maximum transmission unit (MTU) auto discovery can discover the
minimum MTU (path MTU) on the network path from the source to the
destination so that TCP can transmit BGP messages based on the path MTU.

Pre-configuration Tasks
Before configuring path MTU auto discovery, complete the following task:

● Configuring Basic BGP Functions

Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bgp { as-number-plain | as-number-dot }

The BGP view is displayed.

Step 3 Run peer { group-name | ipv4-address } path-mtu auto-discovery

Path MTU auto discovery is enabled.

By default, path MTU auto discovery is disabled.

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NOTE

The transmit and receive paths between two BGP peers may be different. Therefore, you are
advised to run this command on both ends so that the two BGP peers can exchange
messages based on the path MTU.

----End

Verifying the Configuration

● Run the display bgp peer [ ipv4-address ] verbose command to check
whether path MTU auto discovery has been successfully configured.

9.17 Configuring MP-BGP

Multiprotocol BGP (MP-BGP) enables BGP to support IPv4 unicast networks, IPv4
multicast networks, and IPv6 unicast networks.

Pre-configuration Tasks
Before configuring MP-BGP, complete the following task:

● 9.6.1 Starting a BGP Process

Procedure
Step 1 Run system-view

The system view is displayed.

Step 2 Run bgp { as-number-plain | as-number-dot }

BGP is started, the local AS number is specified, and the BGP view is displayed.

Step 3 Enter the corresponding address family view based on network type to configure
BGP devices on networks.
● Run ipv4-family unicast
The BGP-IPv4 unicast address family view is displayed.
● Run ipv4-family vpnv4
The BGP-VPNv4 address family view is displayed.
● Run ipv4-family vpn-instance vpn-instance-name
The BGP-VPN instance IPv4 address family view is displayed.
● Run ipv4-family multicast
The BGP-IPv4 multicast address family view is displayed.
● Run ipv6-family unicast
The BGP-IPv6 unicast address family view is displayed.

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NOTE

● Different extended BGP functions must be configured in their respective address family
views, while common BGP functions are configured in the BGP view.
● The Router supports the following MBGP features: basic BGP functions, BGP security
(MD5 authentication and keychain authentication), simplifying IBGP network
connections (route reflector and confederation), BGP route selection and load balancing,
controlling the receiving and advertisement of BGP routes, adjusting the BGP network
convergence speed, BGP reliability, BGP route summarization, path MTU auto discovery,
and advertising default routes to peers.
● Some BGP4+ functions can be configured in the BGP view, and some BGP4+ functions
need to be configured in the IPv6 unicast address family view. For example, the
following BGP4+ functions need to be configured in the IPv6 unicast address family
view: load balancing, manual route summarization, route dampening, community, and
route reflector.

----End

9.18 Configuring the Dynamic BGP Peer Function

Usage Scenario
If static BGP peers change frequently, the local device needs to add or delete BGP
peer configurations in response to each change, which requires a heavy
maintenance workload. To address this problem, configure the dynamic BGP peer
function, which allows BGP to listen to BGP connection requests from a specified
network segment, establish BGP peer relationships dynamically, and add the peers
to a peer group. This spares the local device from adding or deleting BGP peer
configurations in response to each change in the peer number, which reduces the
maintenance workload.

Pre-configuration Tasks
Before configuring the dynamic BGP peer function, configure basic BGP
functions.

Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 (Optional) Run bgp dynamic-session-limit limit-value
The maximum number of dynamic BGP peer sessions is configured.
If a large number of dynamic BGP peer sessions are established on the network
segment, excessive system resources will be consumed. To prevent this problem,
configure a maximum number for dynamic BGP peer sessions as required.
By default, the maximum number of dynamic BGP peer sessions is half of the
total specification.

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Step 4 (Optional) Run ipv4-family vpn-instance vpn-instance-name

The BGP-VPN instance IPv4 address family view is displayed.
Perform this step if you need to configure the dynamic BGP peer function in the
BGP-VPN instance IPv4 address family view in a BGP/MPLS IP VPN scenario.
Step 5 Run group group-name [ external | internal ]
A BGP peer group is created.
Configure the following parameters as required:
● If the local device and its peers reside in the same AS, configure internal to
create an IBGP peer group.
● If the local device and its peers reside in different ASs, configure external to
create an EBGP peer group.
If neither internal nor external is configured, an IBGP peer group is created by
default.
Step 6 Run peer group-name listen-net network { mask | mask-length }
BGP is configured to listen to BGP connection requests from a specified network
segment and establish BGP peer relationships dynamically.
If you run the command multiple times, BGP listens to BGP connection requests
from multiple network segments.
Step 7 Run peer group-name as-number { as-number-plain | as-number-dot }
[ optional-as { optional-as-number-plain | optional-as-number-dot } &<1-5> ]
An AS number is configured for the peer group.
Configure the following parameters as required:
● If the dynamic peers in the peer group reside in the same AS, configure { as-
number-plain | as-number-dot } to set a fixed AS number.
● If the dynamic peers in the peer group may reside in different ASs, in addition
to a fixed AS number, you need to configure optional-as { optional-as-
number-plain | optional-as-number-dot } &<1-5> to set an optional AS
number. A maximum of five optional AS numbers can be set.

----End

Verifying the Configuration

After configuring the dynamic BGP peer function, check the configuration.
● Run the display bgp [ vpnv4 { all | vpn-instance vpn-instance-name } ] peer
[ [ ipv4-address ] verbose ] command to check BGP peer information.
● Run the display bgp [ vpnv4 { all | vpn-instance vpn-instance-name } ]
group [ group-name ] command to check BGP peer group information.
# Display BGP peer information. The command output shows dynamic peer
information.
<Huawei> display bgp peer
Status codes: * - Dynamic
BGP local router ID : 1.2.3.4

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Local AS number : 10
Total number of peers : 2 Peers in established state : 1
Total number of dynamic peers : 1
Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv

1.1.1.1 4 100 0 0 0 00:00:07 Idle 0

*1.2.5.6 4 200 32 35 0 00:17:49 Established 0

# Display BGP peer group information. The command output shows dynamic peer
information and the network segment from which BGP listens to BGP connection
requests.
<Huawei> display bgp group my-peer
BGP peer-group: my-peer
Remote AS: 100

listen-net: 10.1.1.0 24

Authentication type configured: None

Group's BFD has been enabled
Type : internal
Maximum allowed route limit: 100
Threshold: 75%
Configured hold timer value: 180
Keepalive timer value: 60
Connect-retry timer value: 32
Minimum route advertisement interval is 15 seconds
PeerSession Members:
10.1.1.2

Status codes: * - Dynamic

Peer Preferred Value: 0

No routing policy is configured
Peer Members:
Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv
*10.1.1.2 4 100 35 42 0 00:29:01 Established 0

9.19 Maintaining BGP

9.19.1 Configuring Alarm and Clear Alarm Thresholds for the

Number of BGP Routes
Alarm and clear alarm thresholds for the number of BGP routes facilitate
maintenance.

Context
The number of BGP routes that can be added to a routing table is limited. If the
number exceeds a limit, new routes cannot be added to the routing table, which
may interrupt services. To address this problem, configure alarm and clear alarm
thresholds for the number of BGP routes. With the alarm and clear alarm
thresholds, alarms are generated and cleared as expected. The alarms prompt you
to check whether an exception occurs and to take preventive measures. You can
configure the alarm and clear alarm thresholds as required.

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Procedure
Step 1 Run system-view
The system view is displayed.
Step 2 Run bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
Step 3 Run routing-table limit threshold-alarm upper-limit upper-limit-value lower-
limit lower-limit-value
Alarm and clear alarm thresholds are configured for the number of BGP routes.
● upper-limit-value specifies the alarm threshold. If the ratio of BGP routes to
the maximum number that is allowed exceeds the alarm threshold, an alarm
is generated.
● lower-limit-value specifies the clear alarm threshold. If the ratio of BGP routes
to the maximum number that is allowed falls below this threshold, the alarm
is cleared.
● upper-limit-value must be greater than lower-limit-value; otherwise, alarms
are generated and cleared repeatedly if route flapping occurs.
By default, upper-limit-value is 80%, and lower-limit-value is 70%.

----End

9.19.2 Resetting BGP Connections

Context

NOTICE

Running the reset bgp command to reset BGP connections will interrupt BGP peer
relationships between BGP devices. Exercise caution when you use this command.

When the BGP routing policy changes, for example, the router does not support
the route-refresh capability, reset BGP connections to make the modification take
effect.

Procedure
● To reset all BGP connections, run the reset bgp all command in the user view.
● To reset the BGP connection with a specified AS, run the reset bgp { as-
number-plain | as-number-dot } command in the user view.
● To reset the BGP connection with a specified peer, run the reset bgp ipv4-
address command in the user view.
● To reset all EBGP connections, run the reset bgp external command in the
user view.
● To reset the BGP connection with a specified peer group, run the reset bgp
group group-name command in the user view.

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● To reset all IBGP connections, run the reset bgp internal command in the
user view.
● To reset the MBGP connection with a specified peer, run the reset bgp
multicast peer-address command in the user view.
● To reset all MBGP connections, run the reset bgp multicast all command in
the user view.
● To reset the MBGP connection with all the peers in a specified peer group, run
the reset bgp multicast group group-name command in the user view.
● To reset all external connections, run the reset bgp multicast external
command in the user view.
● To reset all internal connections, run the reset bgp multicast internal
command in the user view.

----End

9.19.3 Clearing BGP Statistics

Context

NOTICE

BGP statistics cannot be restored after being cleared. Exercise caution when you
reset BGP statistics.

Procedure
● To clear route flapping statistics, run the reset bgp flap-info [ regexp as-
path-regexp | as-path-filter as-path-filter-number | ipv4-address [ mask |
mask-length ] ] command in the user view.
● To clear route flapping statistics on a specified peer, run the reset bgp ipv4-
address flap-info command in the user view.
● To clear route dampening statistics and release suppressed routes, run the
reset bgp dampening [ ipv4-address [ mask | mask-length ] ] command in
the user view.
● To clear MBGP route dampening statistics, run the reset bgp multicast
dampening [ ip-address [ mask | mask-length ] ] command in the user view.
● To clear MBGP route flapping statistics, run the reset bgp multicast flap-info
[ ip-address [ mask | mask-length ] | as-path-filter { as-path-list-number | as-
path-list-name } | regrexp regrexp ] command in the user view.

----End

9.20 Configuration Examples for BGP

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9.20.1 Example for Configuring Basic BGP Functions

Networking Requirements
As shown in Figure 9-26, BGP runs between Routers; an EBGP connection is
established between Router A and Router B; IBGP full-mesh connections are
established between Router B, Router C, and Router D.

Figure 9-26 Networking diagram of configuring basic BGP functions

RouterC
AS 65008 AS 65009
GE3/0/0 GE2/0/0
9.1.3.2/24 9.1.2.1/24
RouterA
GE2/0/0
200.1.1.2/24
GE3/0/0 GE2/0/0
GE1/0/0 9.1.3.1/24 9.1.2.2/24
GE1/0/0
8.1.1.1/8 9.1.1.1/24
GE2/0/0
GE1/0/0
200.1.1.1/24
RouterB 9.1.1.2/24 RouterD

Configuration Roadmap
The configuration roadmap is as follows:
1. Configure IBGP connections between Router B, Router C, and Router D.
2. Configure an EBGP connection between Router A and Router B.

Procedure
Step 1 Configure an IP address for each interface.
# Configure Router A.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 8.1.1.1 8
[RouterA-GigabitEthernet1/0/0] quit

The configurations of Router B, Router C, and Router D are similar to the

configuration of Router A, and are not mentioned here.
Step 2 Configure IBGP connections.
# Configure Router B.
[RouterB] bgp 65009
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 9.1.1.2 as-number 65009
[RouterB-bgp] peer 9.1.3.2 as-number 65009

# Configure Router C.

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[RouterC] bgp 65009

[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 9.1.3.1 as-number 65009
[RouterC-bgp] peer 9.1.2.2 as-number 65009
[RouterC-bgp] quit

# Configure Router D.
[RouterD] bgp 65009
[RouterD-bgp] router-id 4.4.4.4
[RouterD-bgp] peer 9.1.1.1 as-number 65009
[RouterD-bgp] peer 9.1.2.1 as-number 65009
[RouterD-bgp] quit

Step 3 Configure an EBGP connection.

# Configure Router A.
[RouterA] bgp 65008
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 200.1.1.1 as-number 65009

# Configure Router B.
[RouterB-bgp] peer 200.1.1.2 as-number 65008

# View the status of BGP peers.

[RouterB-bgp] display bgp peer
BGP local router ID : 2.2.2.2
Local AS number : 65009
Total number of peers : 3 Peers in established state : 3
Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv
9.1.1.2 4 65009 49 62 0 00:44:58 Established 0
9.1.3.2 4 65009 56 56 0 00:40:54 Established 0
200.1.1.2 4 65008 49 65 0 00:44:03 Established 1

The preceding command output shows that BGP connections have been
established between Router B and other Routers.
Step 4 Configure Router A to advertise route 8.0.0.0/8.
# Configure Router A to advertise a route.
[RouterA-bgp] ipv4-family unicast
[RouterA-bgp-af-ipv4] network 8.0.0.0 255.0.0.0
[RouterA-bgp-af-ipv4] quit

# View the routing table of Router A.

[RouterA-bgp] display bgp routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 8.0.0.0 0.0.0.0 0 0 i

# View the routing table of Router B.

[RouterB-bgp] display bgp routing-table

BGP Local router ID is 2.2.2.2

Status codes: * - valid, > - best, d - damped,

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h - history, i - internal, s - suppressed, S - Stale

Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 8.0.0.0 200.1.1.2 0 0 65008i

# View the routing table of Router C.

[RouterC] display bgp routing-table

BGP Local router ID is 3.3.3.3

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

Network NextHop MED LocPrf PrefVal Path/Ogn

i 8.0.0.0 200.1.1.2 0 100 0 65008i

NOTE

The preceding command output shows that Router C has learned the route to destination
8.0.0.0 in AS 65008. The route, however, is invalid because the next hop 200.1.1.2 of this
route is unreachable.

Step 5 Configure BGP to import direct routes.

# Configure Router B.
[RouterB-bgp] ipv4-family unicast
[RouterB-bgp-af-ipv4] import-route direct

# View the BGP routing table of Router A.

[RouterA-bgp] display bgp routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 4

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 8.0.0.0 0.0.0.0 0 0 i

*> 9.1.1.0/24 200.1.1.1 0 0 65009?
*> 9.1.3.0/24 200.1.1.1 0 0 65009?
200.1.1.0 200.1.1.1 0 0 65009?

# View the BGP routing table of Router C.

[RouterC] display bgp routing-table

BGP Local router ID is 3.3.3.3

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 4

Network NextHop MED LocPrf PrefVal Path/Ogn

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*>i 8.0.0.0 200.1.1.2 0 100 0 65008i

*>i 9.1.1.0/24 9.1.3.1 0 100 0 ?
i 9.1.3.0/24 9.1.3.1 0 100 0 ?
*>i 200.1.1.0 9.1.3.1 0 100 0 ?

The preceding command output shows that the route to destination 8.0.0.0
becomes valid because the next-hop address of this route is the address of Router
A.
# Run the ping command on Router C.
[RouterC] ping 8.1.1.1
PING 8.1.1.1: 56 data bytes, press CTRL_C to break
Reply from 8.1.1.1: bytes=56 Sequence=1 ttl=254 time=31 ms
Reply from 8.1.1.1: bytes=56 Sequence=2 ttl=254 time=47 ms
Reply from 8.1.1.1: bytes=56 Sequence=3 ttl=254 time=31 ms
Reply from 8.1.1.1: bytes=56 Sequence=4 ttl=254 time=16 ms
Reply from 8.1.1.1: bytes=56 Sequence=5 ttl=254 time=31 ms
--- 8.1.1.1 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 16/31/47 ms

----End

Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
interface GigabitEthernet1/0/0
ip address 8.1.1.1 255.0.0.0
#
interface GigabitEthernet2/0/0
ip address 200.1.1.2 255.255.255.0
#
bgp 65008
router-id 1.1.1.1
peer 200.1.1.1 as-number 65009
#
ipv4-family unicast
undo synchronization
network 8.0.0.0
peer 200.1.1.1 enable
#
return
● Configuration file of Router B
#
sysname RouterB
#
interface GigabitEthernet1/0/0
ip address 9.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.1.1 255.255.255.0
#
interface GigabitEthernet3/0/0
ip address 9.1.3.1 255.255.255.0
#
bgp 65009
router-id 2.2.2.2
peer 9.1.1.2 as-number 65009
peer 9.1.3.2 as-number 65009
peer 200.1.1.2 as-number 65008
#

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ipv4-family unicast
undo synchronization
import-route direct
peer 9.1.1.2 enable
peer 9.1.3.2 enable
peer 200.1.1.2 enable
#
return

● Configuration file of Router C

#
sysname RouterC
#
interface GigabitEthernet2/0/0
ip address 9.1.2.1 255.255.255.0
#
interface GigabitEthernet3/0/0
ip address 9.1.3.2 255.255.255.0
#
bgp 65009
router-id 3.3.3.3
peer 9.1.2.2 as-number 65009
peer 9.1.3.1 as-number 65009
#
ipv4-family unicast
undo synchronization
peer 9.1.2.2 enable
peer 9.1.3.1 enable
#
return

● Configuration file of Router D

#
sysname RouterD
#
interface GigabitEthernet1/0/0
ip address 9.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 9.1.2.2 255.255.255.0
#
bgp 65009
router-id 4.4.4.4
peer 9.1.1.1 as-number 65009
peer 9.1.2.1 as-number 65009
#
ipv4-family unicast
undo synchronization
peer 9.1.1.1 enable
peer 9.1.2.1 enable
#
return

9.20.2 Example for Configuring Basic BGP4+ Functions

Networking Requirements
As shown in Figure 9-27, there are two ASs: 65008 and 65009. Router A belongs
to AS 65008; Router B, and Router C belong to AS65009. Routing Protocol is
required to exchange the routing information between the two ASs.

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Figure 9-27 Figure 1 Networking diagram of configuring basic BGP4+ functions

AS 65008 AS 65009
GE1/0/0
8::1/64 GE1/0/0
9:1::1/64
GE2/0/0 GE2/0/0 GE1/0/0
RouterA 10::2/64 10::1/64 RouterB 9:1::2/64 RouterC

Configuration Roadmap
The configuration roadmap is as follows:
1. Configure the IBGP connection between Router B and Router C.
2. Configure the EBGP connection between Router A and Router B.

Procedure
Step 1 Assign an IPv6 address for each interface.
# Configure IPv6 addresses for interfaces on RouterA.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] ipv6
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ipv6 enable
[RouterA-GigabitEthernet1/0/0] ipv6 address 8::1/64
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet1/0/0] ipv6 enable
[RouterA-GigabitEthernet1/0/0] ipv6 address 10::2/64

The configurations of RouterB and RouterC are similar to the configuration of

RouterA, and are not mentioned here.
Step 2 Configure the IBGP.
# Configure Router B.
[RouterB] ipv6
[RouterB] bgp 65009
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 9:1::2 as-number 65009
[RouterB-bgp] ipv6-family unicast
[RouterB-bgp-af-ipv6] peer 9:1::2 enable
[RouterB-bgp-af-ipv6] network 9:1:: 64

# Configure Router C.
[RouterC] ipv6
[RouterC] bgp 65009
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 9:1::1 as-number 65009
[RouterC-bgp] ipv6-family unicast
[RouterC-bgp-af-ipv6] peer 9:1::1 enable
[RouterC-bgp-af-ipv6] network 9:1:: 64

Step 3 Configure the EBGP.

# Configure Router A.

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[RouterA] ipv6
[RouterA] bgp 65008
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 10::1 as-number 65009
[RouterA-bgp] ipv6-family unicast
[RouterA-bgp-af-ipv6] peer 10::1 enable
[RouterA-bgp-af-ipv6] network 10:: 64
[RouterA-bgp-af-ipv6] network 8:: 64

# Configure Router B.
[RouterB] bgp 65009
[RouterB-bgp] peer 10::2 as-number 65008
[RouterB-bgp] ipv6-family unicast
[RouterB-bgp-af-ipv6] peer 10::2 enable
[RouterB-bgp-af-ipv6] network 10:: 64

# Check the connection status of BGP4+ peers.

[RouterB] display bgp ipv6 peer

BGP local router ID : 2.2.2.2

Local AS number : 65009
Total number of peers : 2 Peers in established state : 2

Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv

9:1::2 4 65009 10 14 0 00:07:10 Established 1

10::2 4 65008 6 6 0 00:02:17 Established 2

The routing table shows that Router B has set up BGP4+ connections with other
routers.
# Display the routing table of Router A.
[RouterA] display bgp ipv6 routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 4

*> Network : 8:: PrefixLen : 64
NextHop : :: LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : i
*> Network : 9:1:: PrefixLen : 64
NextHop : 10::1 LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : 65009 i
*> Network : 10:: PrefixLen : 64
NextHop : :: LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : i

NextHop : 10::1 LocPrf :

MED :0 PrefVal : 0
Label :
Path/Ogn : 65009 i

The routing table shows that Router A has learned the route from AS 65009. AS
65008 and AS 65009 can exchange their routing information.

----End

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Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
ipv6
#
interface GigabitEthernet1/0/0
ipv6 enable
ipv6 address 8::1/64
#
interface GigabitEthernet2/0/0
ipv6 enable
ipv6 address 10::2/64
#
bgp 65008
router-id 1.1.1.1
peer 10::1 as-number 65009
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 8:: 64
network 10:: 64
peer 10::1 enable
#
return
● Configuration file of Router B
#
sysname RouterB
#
ipv6
#
interface GigabitEthernet1/0/0
ipv6 enable
ipv6 address 9:1::1/64
#
interface GigabitEthernet2/0/0
ipv6 enable
ipv6 address 10::1/64
#
bgp 65009
router-id 2.2.2.2
peer 9:1::2 as-number 65009
peer 10::2 as-number 65008
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 9:1:: 64
network 10:: 64
peer 9:1::2 enable
peer 10::2 enable
#
return
● Configuration file of Router C
#
sysname RouterC
#
ipv6
#
interface GigabitEthernet1/0/0

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ipv6 enable
ipv6 address 9:1::2/64
#
bgp 65009
router-id 3.3.3.3
peer 9:1::1 as-number 65009
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 9:1:: 64
peer 9:1::1 enable
#
return

9.20.3 Example for Configuring Basic MBGP Functions

Networking Requirements
As shown in Figure 9-28, the receiver receives VoD information in multicast mode.
The receiver and the source reside in different ASs. Multicast routing information
needs to be transmitted between ASs.

Figure 9-28 Networking diagram of configuring MBGP

AS100 AS200
RouterD
Loopback0
GE2/0/0
GE1/0/0

Source RouterA RouterB GE2/0/0

GE2/0/0 GE1/0/0
GE1/0/0 GE3/0/0

Loopback0 Loopback0
GE1/0/0
GE3/0/0
RouterC Loopback0
GE2/0/0
Receiver

MBGP peers

Device Interface IP Address Device Interface IP Address

RouterA GE1/0/0 10.1.1.1/24 RouterC GE1/0/0 10.4.1.1/24

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Device Interface IP Address Device Interface IP Address

GE2/0/0 10.10.10.1/ GE2/0/0 10.168.1.1/

24 24

Loopback0 1.1.1.1/32 GE3/0/0 10.2.1.1/24

RouterB GE1/0/0 10.1.1.2/24 Loopback0 3.3.3.3/32

GE2/0/0 10.3.1.2/24 RouterD GE1/0/0 10.4.1.2/24

GE3/0/0 10.2.1.2/24 GE2/0/0 10.3.1.1/24

Loopback0 2.2.2.2/32 Loopback0 4.4.4.4/32

Configuration Roadmap
The configuration roadmap is as follows:
1. Configure MBGP peers for inter-AS multicast transmission.
2. Configure the routes advertised by MBGP.
3. Enable the multicast function on each router.
4. Configure basic PIM-SM functions on each router in ASs and enable IGMP on
receiver-side interfaces.
5. Configure a BSR boundary on the interfaces that connect to two ASs.
6. Configure MSDP peers to transmit inter-domain multicast source information.

Procedure
Step 1 Assign IP addresses to the interfaces on each router and configure OSPF in ASs.
# Configure IP addresses and masks for the interfaces on each router according to
Figure 9-28 and configure OSPF on the routers in ASs. Ensure that Router B,
Router C, Router D can communicate with the receiver at the network layer, learn
routes to the loopback interfaces of each other, and dynamically update routes
using a unicast routing protocol. Configure OSPF process 1. The configuration
procedure is not mentioned here.
Step 2 Configure BGP, enable the MBGP protocol, and configure MBGP peers.
# Configure BGP and the MBGP peer on Router A.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] bgp 100
[RouterA-bgp] peer 10.1.1.2 as-number 200
[RouterA-bgp] ipv4-family multicast
[RouterA-bgp-af-multicast] peer 10.1.1.2 enable
[RouterA-bgp-af-multicast] quit
[RouterA-bgp] quit

# Configure BGP and the MBGP peer on Router B.

[RouterB] bgp 200
[RouterB-bgp] peer 10.1.1.1 as-number 100
[RouterB-bgp] peer 10.2.1.1 as-number 200

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[RouterB-bgp] peer 10.3.1.1 as-number 200

[RouterB-bgp] ipv4-family multicast
[RouterB-bgp-af-multicast] peer 10.1.1.1 enable
[RouterB-bgp-af-multicast] peer 10.2.1.1 enable
[RouterB-bgp-af-multicast] peer 10.3.1.1 enable
[RouterB-bgp-af-multicast] quit
[RouterB-bgp] quit

# Configure BGP and the MBGP peer on Router C.

[RouterC] bgp 200
[RouterC-bgp] peer 10.2.1.2 as-number 200
[RouterC-bgp] peer 10.4.1.2 as-number 200
[RouterC-bgp] ipv4-family multicast
[RouterC-bgp-af-multicast] peer 10.2.1.2 enable
[RouterC-bgp-af-multicast] peer 10.4.1.2 enable
[RouterC-bgp-af-multicast] quit
[RouterC-bgp] quit

# Configure BGP and the MBGP peer on Router D.

[RouterD] bgp 200
[RouterD-bgp] peer 10.3.1.2 as-number 200
[RouterD-bgp] peer 10.4.1.1 as-number 200
[RouterD-bgp] ipv4-family multicast
[RouterD-bgp-af-multicast] peer 10.3.1.2 enable
[RouterD-bgp-af-multicast] peer 10.4.1.1 enable
[RouterD-bgp-af-multicast] quit
[RouterD-bgp] quit

Step 3 Configure the routes to be advertised.

# Configure the routes to be advertised on Router A.
[RouterA] bgp 100
[RouterA-bgp] import-route direct
[RouterA-bgp] ipv4-family multicast
[RouterA-bgp-af-multicast] import-route direct
[RouterA-bgp-af-multicast] quit
[RouterA-bgp] quit

# Configure the routes to be advertised on Router B.

[RouterB] bgp 200
[RouterB-bgp] import-route direct
[RouterB-bgp] import-route ospf 1
[RouterB-bgp] ipv4-family multicast
[RouterB-bgp-af-multicast] import-route direct
[RouterB-bgp-af-multicast] import-route ospf 1
[RouterB-bgp-af-multicast] quit
[RouterB-bgp] quit

# Configure the routes to be advertised on Router C. The configuration of Router

D is similar to the configuration of Router C, and is not mentioned here.
[RouterC] bgp 200
[RouterC-bgp] import-route direct
[RouterC-bgp] ipv4-family multicast
[RouterC-bgp-af-multicast] import-route direct
[RouterC-bgp-af-multicast] import-route ospf 1
[RouterC-bgp-af-multicast] quit
[RouterC-bgp] quit

Step 4 Enable the multicast function on each Router and interfaces on the Routers.
# Configure Router A.
[RouterA] multicast routing-enable
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] pim sm

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[RouterA-GigabitEthernet1/0/0] quit
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet2/0/0] pim sm
[RouterA-GigabitEthernet2/0/0] quit

# Configure Router B.
[RouterB] multicast routing-enable
[RouterB] interface gigabitethernet 1/0/0
[RouterB-GigabitEthernet1/0/0] pim sm
[RouterB-GigabitEthernet1/0/0] quit
[RouterB] interface gigabitethernet 2/0/0
[RouterB-GigabitEthernet2/0/0] pim sm
[RouterB-GigabitEthernet2/0/0] quit
[RouterB] interface gigabitethernet 3/0/0
[RouterB-GigabitEthernet3/0/0] pim sm
[RouterB-GigabitEthernet3/0/0] quit

# Configure Router C.
[RouterC] multicast routing-enable
[RouterC] interface gigabitethernet 1/0/0
[RouterC-GigabitEthernet1/0/0] pim sm
[RouterC-GigabitEthernet1/0/0] quit
[RouterC] interface gigabitethernet 2/0/0
[RouterC-GigabitEthernet2/0/0] pim sm
[RouterC-GigabitEthernet2/0/0] igmp enable
[RouterC-GigabitEthernet2/0/0] quit
[RouterC] interface gigabitethernet 3/0/0
[RouterC-GigabitEthernet3/0/0] pim sm
[RouterC-GigabitEthernet3/0/0] quit

# Configure Router D.
[RouterD] multicast routing-enable
[RouterD] interface gigabitethernet 1/0/0
[RouterD-GigabitEthernet1/0/0] pim sm
[RouterD-GigabitEthernet1/0/0] quit
[RouterD] interface gigabitethernet 2/0/0
[RouterD-GigabitEthernet2/0/0] pim sm
[RouterD-GigabitEthernet2/0/0] quit

Step 5 Configure the BSR and RP within each AS.

# Configure Router A.
[RouterA] interface loopback 0
[RouterA-LoopBack0] ip address 1.1.1.1 255.255.255.255
[RouterA-LoopBack0] pim sm
[RouterA-LoopBack0] quit
[RouterA] pim
[RouterA-pim] c-bsr loopback 0
[RouterA-pim] c-rp loopback 0
[RouterA-pim] quit

# Configure Router B.
[RouterB] interface loopback 0
[RouterB-LoopBack0] ip address 2.2.2.2 255.255.255.255
[RouterB-LoopBack0] pim sm
[RouterB-LoopBack0] quit
[RouterB] pim
[RouterB-pim] c-bsr loopback 0
[RouterB-pim] c-rp loopback 0
[RouterB-pim] quit

Step 6 Configure a BSR boundary on the interfaces that connect to two ASs.

# Configure Router A.

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[RouterA] interface gigabitethernet 1/0/0

[RouterA-GigabitEthernet1/0/0] pim bsr-boundary
[RouterA-GigabitEthernet1/0/0] quit

# Configure Router B.
[RouterB] interface gigabitethernet 1/0/0
[RouterB-GigabitEthernet1/0/0] pim bsr-boundary
[RouterB-GigabitEthernet1/0/0] quit

Step 7 Configure MSDP peers.

# Configure Router A.
[RouterA] msdp
[RouterA-msdp] peer 10.1.1.2 connect-interface gigabitethernet 1/0/0
[RouterA-msdp] quit

# Configure Router B.
[RouterB] msdp
[RouterB-msdp] peer 10.1.1.1 connect-interface gigabitethernet 1/0/0
[RouterB-msdp] quit

Step 8 Verify the configuration.

# Run the display bgp multicast peer command to view the MBGP peer
relationship between Routers. For example, information about the MBGP peer
relationship on Router A is as follows:
[RouterA] display bgp multicast peer
BGP local router ID : 1.1.1.1
Local AS number : 100
Total number of peers : 1 Peers in established state : 1
Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv
10.1.1.2 4 200 82 75 0 00:30:29 Established 17

# Run the display msdp brief command to view information about the MSDP
peer relationship between Routers. For example, brief information about the
MSDP peer relationship on Router B is as follows:
[RouterB] display msdp brief
MSDP Peer Brief Information of VPN-Instance: public net
Configured Up Listen Connect Shutdown Down
1 1 0 0 0 0
Peer's Address State Up/Down time AS SA Count Reset Count
10.1.1.1 Up 00:07:17 100 1 0

----End

Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
multicast routing-enable
#
interface GigabitEthernet1/0/0
ip address 10.1.1.1 255.255.255.0
pim bsr-boundary
pim sm
#
interface GigabitEthernet2/0/0
ip address 10.10.10.1 255.255.255.0
pim sm
#

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interface Loopback0
ip address 1.1.1.1 255.255.255.255
pim sm
#
pim
c-bsr Loopback0
c-rp Loopback0
#
bgp 100
peer 10.1.1.2 as-number 200
#
ipv4-family unicast
undo synchronization
import-route direct
peer 10.1.1.2 enable
#
ipv4-family multicast
undo synchronization
import-route direct
peer 10.1.1.2 enable
#
msdp
peer 10.1.1.2 connect-interface GigabitEthernet1/0/0
#
return
● Configuration file of Router B
#
sysname RouterB
#
multicast routing-enable
#
interface GigabitEthernet1/0/0
ip address 10.1.1.2 255.255.255.0
pim bsr-boundary
pim sm
#
interface GigabitEthernet2/0/0
ip address 10.3.1.2 255.255.255.0
pim sm
#
interface GigabitEthernet3/0/0
ip address 10.2.1.2 255.255.255.0
pim sm
#
interface Loopback0
ip address 2.2.2.2 255.255.255.255
pim sm
#
pim
c-bsr Loopback0
c-rp Loopback0
#
ospf 1
area 0.0.0.0
network 10.2.1.0 0.0.0.255
network 10.3.1.0 0.0.0.255
network 2.2.2.2 0.0.0.0
#
bgp 200
peer 10.1.1.1 as-number 100
peer 10.2.1.1 as-number 200
peer 10.3.1.1 as-number 200
#
ipv4-family unicast
undo synchronization
import-route direct
import-route ospf 1
peer 10.1.1.1 enable
peer 10.2.1.1 enable

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peer 10.3.1.1 enable

#
ipv4-family multicast
undo synchronization
import-route direct
import-route ospf 1
peer 10.1.1.1 enable
peer 10.2.1.1 enable
peer 10.3.1.1 enable
#
msdp
peer 10.1.1.1 connect-interface GigabitEthernet1/0/0
#
return
● Configuration file of Router C
#
sysname RouterC
#
multicast routing-enable
#
interface GigabitEthernet1/0/0
ip address 10.4.1.1 255.255.255.0
pim sm
#
interface GigabitEthernet2/0/0
ip address 10.168.1.1 255.255.255.0
pim sm
igmp enable
#
interface GigabitEthernet3/0/0
ip address 10.2.1.1 255.255.255.0
pim sm
#
interface Loopback0
ip address 3.3.3.3 255.255.255.255
pim sm
#
ospf 1
area 0.0.0.0
network 10.2.1.0 0.0.0.255
network 10.4.1.0 0.0.0.255
network 10.168.1.0 0.0.0.255
network 3.3.3.3 0.0.0.0
#
bgp 200
peer 10.2.1.2 as-number 200
peer 10.4.1.2 as-number 200
#
ipv4-family unicast
undo synchronization
import-route direct
peer 10.2.1.2 enable
peer 10.4.1.2 enable
#
ipv4-family multicast
undo synchronization
import-route direct
import-route ospf 1
peer 10.2.1.2 enable
peer 10.4.1.2 enable
#
return
● Configuration file of Router D
#
sysname RouterD
#
multicast routing-enable
#

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interface GigabitEthernet1/0/0
ip address 10.4.1.2 255.255.255.0
pim sm
#
interface GigabitEthernet2/0/0
ip address 10.3.1.1 255.255.255.0
pim sm
#
interface Loopback0
ip address 4.4.4.4 255.255.255.255
pim sm
#
ospf 1
area 0.0.0.0
network 10.3.1.0 0.0.0.255
network 10.4.1.0 0.0.0.255
network 4.4.4.4 0.0.0.0
#
bgp 200
peer 10.3.1.2 as-number 200
peer 10.4.1.1 as-number 200
#
ipv4-family unicast
undo synchronization
import-route direct
peer 10.3.1.2 enable
peer 10.4.1.1 enable
#
ipv4-family multicast
undo synchronization
import-route direct
import-route ospf 1
peer 10.3.1.2 enable
peer 10.4.1.1 enable
#
return

9.20.4 Example for Configuring BGP to Interact with an IGP

Networking Requirements
The network shown in Figure 9-29 is divided into AS 65008 and AS 65009. In AS
65009, an IGP is used to calculate routes. In this example, OSPF is used as an IGP.
The two ASs need to communicate with each other.

Figure 9-29 Networking diagram for configuring BGP to interact with an IGP

GE1/0/0 GE1/0/0 GE2/0/0

GE2/0/0 9.1.2.1/24
8.1.1.1/24 3.1.1.2/24 9.1.1.1/24

GE1/0/0
GE2/0/0
RouterA RouterB 9.1.1.2/24 RouterC
3.1.1.1/24
AS 65008
AS 65009

Configuration Roadmap
The configuration roadmap is as follows:

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1. Configure OSPF on Routers B and C so that these devices can access each
other.
2. Establish an EBGP connection between Routers A and B so that these devices
can exchange routing information.
3. Configure BGP and OSPF to import routes from each other on Router B so
that the two ASs can communicate with each other.
4. (Optional) Configure BGP route summarization on Router B to simplify the
BGP routing table.

Procedure
Step 1 Configure an IP address for each interface.

Configure an IP address to each interface as shown in Figure 9-29. For details

about the configuration, see the following configuration files.

Step 2 Configuring OSPF

# Configure Router B.
<Huawei> system-view
[Huawei] sysname RouterB
[RouterB] ospf 1
[RouterB-ospf-1] area 0
[RouterB-ospf-1-area-0.0.0.0] network 9.1.1.0 0.0.0.255
[RouterB-ospf-1-area-0.0.0.0] quit
[RouterB-ospf-1] quit

# Configure Router C.
[RouterC] ospf 1
[RouterC-ospf-1] area 0
[RouterC-ospf-1-area-0.0.0.0] network 9.1.1.0 0.0.0.255
[RouterC-ospf-1-area-0.0.0.0] network 9.1.2.0 0.0.0.255
[RouterC-ospf-1-area-0.0.0.0] quit
[RouterC-ospf-1] quit

Step 3 Establish an EBGP connection.

# Configure Router A.
[RouterA] bgp 65008
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 3.1.1.1 as-number 65009
[RouterA-bgp] ipv4-family unicast
[RouterA-bgp-af-ipv4] network 8.1.1.0 255.255.255.0

# Configure Router B.
[RouterB] bgp 65009
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 3.1.1.2 as-number 65008

Step 4 Configure BGP to interact with an IGP

# On Router B, configure BGP to import OSPF routes.

[RouterB-bgp] ipv4-family unicast
[RouterB-bgp-af-ipv4] import-route ospf 1
[RouterB-bgp-af-ipv4] quit
[RouterB-bgp] quit

# View the routing table of Router A.

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[RouterA] display bgp routing-table

BGP Local router ID is 1.1.1.1
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Total Number of Routes: 3
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 8.1.1.0/24 0.0.0.0 0 0 i
*> 9.1.1.0/24 3.1.1.1 0 0 65009?
*> 9.1.2.0/24 3.1.1.1 2 0 65009?

# On Router B, configure OSPF to import BGP routes.

[RouterB] ospf
[RouterB-ospf-1] import-route bgp
[RouterB-ospf-1] quit

# View the routing table of Router C.

[RouterC] display ip routing-table
Route Flags:
R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 7 Routes : 7

Destination/Mask Proto Pre Cost Flags NextHop Interface

8.1.1.0/24 O_ASE 150 1 D 9.1.1.1 GigabitEthernet1/0/0

9.1.1.0/24 Direct 0 0 D 9.1.1.2 GigabitEthernet1/0/0
9.1.1.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet1/0/0
9.1.2.0/24 Direct 0 0 D 9.1.2.1 GigabitEthernet2/0/0
9.1.2.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet2/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0

Step 5 (Optional) Configure automatic route summarization.

BGP is used to transmit routing information on large-scale networks. BGP route
summarization can be configured to simplify routing tables of devices on these
networks.
# Configure Router B.
[RouterB] bgp 65009
[RouterB-bgp] ipv4-family unicast
[RouterB-bgp-af-ipv4] summary automatic

# View the routing table of Router A.

[RouterA] display bgp routing-table
BGP Local router ID is 1.1.1.1
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Total Number of Routes: 2
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 8.1.1.0/24 0.0.0.0 0 0 i
*> 9.0.0.0 3.1.1.1 0 65009?

# Run the ping -a 8.1.1.1 9.1.2.1 command on Router A.

[RouterA] ping -a 8.1.1.1 9.1.2.1
PING 9.1.2.1: 56 data bytes, press CTRL_C to break
Reply from 9.1.2.1: bytes=56 Sequence=1 ttl=254 time=15 ms
Reply from 9.1.2.1: bytes=56 Sequence=2 ttl=254 time=31 ms
Reply from 9.1.2.1: bytes=56 Sequence=3 ttl=254 time=47 ms
Reply from 9.1.2.1: bytes=56 Sequence=4 ttl=254 time=46 ms
Reply from 9.1.2.1: bytes=56 Sequence=5 ttl=254 time=47 ms

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--- 9.1.2.1 ping statistics ---

5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 15/37/47 ms

----End

Configuration Files
● Configuration file of Router A
#
sysname Router A
#
interface GigabitEthernet1/0/0
ip address 8.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 3.1.1.2 255.255.255.0
#
bgp 65008
router-id 1.1.1.1
peer 3.1.1.1 as-number 65009
#
ipv4-family unicast
undo synchronization
network 8.1.1.0 255.255.255.0
peer 3.1.1.1 enable
#
return

● Configuration file of Router B

#
sysname Router B
#
interface GigabitEthernet1/0/0
ip address 9.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 3.1.1.1 255.255.255.0
#
bgp 65009
router-id 2.2.2.2
peer 3.1.1.2 as-number 65008
#
ipv4-family unicast
undo synchronization
summary automatic
import-route ospf 1
peer 3.1.1.2 enable
#
ospf 1
import-route bgp
area 0.0.0.0
network 9.1.1.0 0.0.0.255
#
return

● Configuration file of Router C

#
sysname Router C
#
interface GigabitEthernet1/0/0
ip address 9.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 9.1.2.1 255.255.255.0
#

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ospf 1
area 0.0.0.0
network 9.1.1.0 0.0.0.255
network 9.1.2.0 0.0.0.255
#
return

9.20.5 Example for Configuring AS_Path Filters

Networking Requirements
On the network shown in Figure 9-30, Router B establishes EBGP connections
with Routers A and C. The user wants to disable the devices in AS 10 from
communicating with devices in AS 30.

Figure 9-30 Networking diagram for configuring AS_Path filters

GE1/0/0
AS 10 9.1.1.1/24
GE2/0/0
200.1.2.1/24
RouterA

EBGP

GE2/0/0 GE2/0/0
200.1.2.2/24 EBGP 200.1.3.2/24
GE1/0/0
GE1/0/0
200.1.3.1/24 RouterC 10.1.1.1/24
RouterB
AS 20 AS 30

Configuration Roadmap
The configuration roadmap is as follows:
1. Establish EBGP connections between Routers A and B and between Routers B
and C and configure these devices to import direct routes so that the ASs can
communicate with each other through these EBGP connections.
2. Configure AS_Path filters on Router B and use filtering rules to prevent AS 20
from advertising routes of AS 30 to AS 10 or routes of AS 10 to AS 30.

Procedure
Step 1 Configure an IP address for each interface.
# Configure IP addresses for all interfaces of Router A.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 9.1.1.1 255.255.255.0
[RouterA-GigabitEthernet1/0/0] quit

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[RouterA] interface gigabitethernet 2/0/0

[RouterA-GigabitEthernet2/0/0] ip address 200.1.2.1 255.255.255.0
[RouterA-GigabitEthernet2/0/0] quit

The configurations of RouterB and RouterC are similar to the configuration of

RouterA, and are not mentioned here.
Step 2 Establish EBGP connections.
# Configure Router A.
[RouterA] bgp 10
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 200.1.2.2 as-number 20
[RouterA-bgp] import-route direct

# Configure Router B.
[RouterB] bgp 20
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 200.1.2.1 as-number 10
[RouterB-bgp] peer 200.1.3.2 as-number 30
[RouterB-bgp] import-route direct
[RouterB-bgp] quit

# Configure Router C.
[RouterC] bgp 30
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 200.1.3.1 as-number 20
[RouterC-bgp] import-route direct
[RouterC-bgp] quit

# View routes advertised by Router B. Routes advertised by Router B to Router C

are used as an example. You can see that Router B advertises the direct route
imported by AS 10.
<RouterB> display bgp routing-table peer 200.1.3.2 advertised-routes

BGP Local router ID is 2.2.2.2

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 5

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 9.1.1.0/24 200.1.3.1 0 20 10?

*> 10.1.1.0/24 200.1.3.1 0 20 30?
*> 200.1.2.0 200.1.3.1 0 0 20?
*> 200.1.2.1/32 200.1.3.1 0 0 20?
*> 200.1.3.0/24 200.1.3.1 0 0 20?

View the routing table of Router C. You can see that Router C has learned the
direct route from Router B.
<RouterC> display bgp routing-table

BGP Local router ID is 3.3.3.3

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 9

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 9.1.1.0/24 200.1.3.1 0 20 10?

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*> 10.1.1.0/24 0.0.0.0 0 0 ?

*> 10.1.1.1/32 0.0.0.0 0 0 ?
*> 127.0.0.0 0.0.0.0 0 0 ?
*> 127.0.0.1/32 0.0.0.0 0 0 ?
*> 200.1.2.0 200.1.3.1 0 0 20?
*> 200.1.3.0/24 0.0.0.0 0 0 ?
* 200.1.3.1 0 0 20?
*> 200.1.3.2/32 0.0.0.0 0 0 ?

Step 3 Configure AS_Path filters on Router B and apply the AS_Path filters to routes to be
advertised by Router B.
# Create AS_Path filter 1 to deny the routes carrying AS number 30. The regular
expression "_30_" indicates any AS list that contains AS 30 and "*" matches any
character.
[RouterB] ip as-path-filter path-filter1 deny _30_
[RouterB] ip as-path-filter path-filter1 permit .*

# Create AS_Path filter 2 to deny the routes carrying AS 10.

[RouterB] ip as-path-filter path-filter2 deny _10_
[RouterB] ip as-path-filter path-filter2 permit .*

# Apply the AS_Path filters to routes to be advertised by Router B.

[RouterB] bgp 20
[RouterB-bgp] peer 200.1.2.1 as-path-filter path-filter1 export
[RouterB-bgp] peer 200.1.3.2 as-path-filter path-filter2 export
[RouterB-bgp] quit

Step 4 # View routes advertised by Router B.

# View routes advertised by Router B to AS 30. You can see that Router B does not
advertise the direct route imported by AS 10.
<RouterB> display bgp routing-table peer 200.1.3.2 advertised-routes

BGP Local router ID is 2.2.2.2

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 2

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 200.1.2.0 200.1.3.1 0 0 20?

*> 200.1.3.0/24 200.1.3.1 0 0 20?

The route does not exist in the BGP routing table of Router C.
<RouterC> display bgp routing-table

BGP Local router ID is 3.3.3.3

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 8

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 10.1.1.0/24 0.0.0.0 0 0 ?

*> 10.1.1.1/32 0.0.0.0 0 0 ?
*> 127.0.0.0 0.0.0.0 0 0 ?
*> 127.0.0.1/32 0.0.0.0 0 0 ?
*> 200.1.2.0 200.1.3.1 0 0 20?

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*> 200.1.3.0/24 0.0.0.0 0 0 ?

* 200.1.3.1 0 0 20?
*> 200.1.3.2/32 0.0.0.0 0 0 ?

# View routes advertised by Router B to AS 10. You can see that Router B does not
advertise the direct route imported by AS 30.
<RouterB> display bgp routing-table peer 200.1.2.1 advertised-routes

BGP Local router ID is 2.2.2.2

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 2

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 200.1.2.0 200.1.2.2 0 0 20?

*> 200.1.3.0/24 200.1.2.2 0 0 20?

The route does not exist in the BGP routing table of Router A.
<RouterA> display bgp routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 8

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 9.1.1.0/24 0.0.0.0 0 0 ?

*> 9.1.1.1/32 0.0.0.0 0 0 ?
*> 127.0.0.0 0.0.0.0 0 0 ?
*> 127.0.0.1/32 0.0.0.0 0 0 ?
*> 200.1.2.0 0.0.0.0 0 0 ?
* 200.1.2.2 0 0 20?
*> 200.1.2.1/32 0.0.0.0 0 0 ?
*> 200.1.3.0/24 200.1.2.2 0 0 20?

----End

Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
interface GigabitEthernet1/0/0
ip address 9.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.1 255.255.255.0
#
bgp 10
router-id 1.1.1.1
peer 200.1.2.2 as-number 20
#
ipv4-family unicast
undo synchronization
import-route direct
peer 200.1.2.2 enable
#
return

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● Configuration file of Router B

#
sysname RouterB
#
interface GigabitEthernet1/0/0
ip address 200.1.3.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.2 255.255.255.0
#
bgp 20
router-id 2.2.2.2
peer 200.1.2.1 as-number 10
peer 200.1.3.2 as-number 30
#
ipv4-family unicast
undo synchronization
import-route direct
peer 200.1.2.1 enable
peer 200.1.2.1 as-path-filter path-filter1 export
peer 200.1.3.2 enable
peer 200.1.3.2 as-path-filter path-filter2 export
#
ip as-path-filter path-filter1 deny _30_
ip as-path-filter path-filter1 permit .*
ip as-path-filter path-filter2 deny _10_
ip as-path-filter path-filter2 permit .*
#
return

● Configuration file of Router C

#
sysname RouterC
#
interface GigabitEthernet1/0/0
ip address 10.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.3.2 255.255.255.0
#
bgp 30
router-id 3.3.3.3
peer 200.1.3.1 as-number 20
#
ipv4-family unicast
undo synchronization
import-route direct
peer 200.1.3.1 enable
#
return

9.20.6 Example for Configuring MED Attributes to Control BGP

Route Selection
Networking Requirements
As shown in Figure 9-31, BGP is configured on all routers; Router A resides in AS
65008; Router B and Router C reside in AS 65009. EBGP connections are
established between Router A and Router B, and between Router A and Router C.
An IBGP connection is established between Router B and Router C. After a period,
traffic from AS 65008 to AS 65009 needs to first pass through RouterC.

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Figure 9-31 Networking diagram for configuring MED attributes of routes to

control route selection

GE2/0/0 RouterB
200.1.1.1/24

GE1/0/0 GE1/0/0
AS 65008 200.1.1.2/24 9.1.1.1/24
EBGP
IBGP
RouterA
AS 65009
GE2/0/0
200.1.2.2/24 EBGP GE1/0/0
9.1.1.2/24

GE2/0/0
200.1.2.1/24 RouterC

Configuration Roadmap
The configuration roadmap is as follows:
1. Establish EBGP connections between Router A and Router B and between
Router A and Router C, and establish an IBGP connection between Router B
and Router C.
2. Apply a routing policy to increase the MED value of the route sent by Router
B to Router A so that Router A will send traffic to AS 65009 through Router C.

Procedure
Step 1 Configure an IP address for each interface.
# Configure IP addresses for all interfaces of RouterA.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 200.1.1.2 255.255.255.0
[RouterA-GigabitEthernet1/0/0] quit
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet2/0/0] ip address 200.1.2.2 255.255.255.0
[RouterA-GigabitEthernet2/0/0] quit

The configurations of RouterB and RouterC are similar to the configuration of

RouterA, and are not mentioned here.
Step 2 Establish BGP connections.
# Configure Router A.
[RouterA] bgp 65008
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 200.1.1.1 as-number 65009
[RouterA-bgp] peer 200.1.2.1 as-number 65009
[RouterA-bgp] quit

# Configure Router B.

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[RouterB] bgp 65009

[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 200.1.1.2 as-number 65008
[RouterB-bgp] peer 9.1.1.2 as-number 65009
[RouterB-bgp] ipv4-family unicast
[RouterB-bgp-af-ipv4] network 9.1.1.0 255.255.255.0
[RouterB-bgp-af-ipv4] quit
[RouterB-bgp] quit

# Configure Router C.
[RouterC] bgp 65009
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 200.1.2.2 as-number 65008
[RouterC-bgp] peer 9.1.1.1 as-number 65009
[RouterC-bgp] ipv4-family unicast
[RouterC-bgp-af-ipv4] network 9.1.1.0 255.255.255.0
[RouterC-bgp-af-ipv4] quit
[RouterC-bgp] quit

# View the routing table of Router A.

[RouterA] display bgp routing-table 9.1.1.0 24

BGP local router ID : 1.1.1.1

Local AS number : 65008
Paths: 2 available, 1 best, 1 select
BGP routing table entry information of 9.1.1.0/24:
From: 200.1.1.1 (2.2.2.2)
Route Duration: 00h00m56s
Direct Out-interface: GigabitEthernet1/0/0
Original nexthop: 200.1.1.1
Qos information : 0x0
AS-path 65009, origin igp, MED 0, pref-val 0, valid, external, best, select, pre 255
Advertised to such 2 peers:
200.1.1.1
200.1.2.1

BGP routing table entry information of 9.1.1.0/24:

From: 200.1.2.1 (3.3.3.3)
Route Duration: 00h00m06s
Direct Out-interface: GigabitEthernet2/0/0
Original nexthop: 200.1.2.1
Qos information : 0x0
AS-path 65009, origin igp, MED 0, pref-val 0, valid, external, pre 255, not preferred for router ID
Not advertised to any peer yet

The preceding command output shows that there are two valid routes to
destination 9.1.1.0/24. The route with the next-hop address of 200.1.1.1 is the
optimal route because the router ID of Router is smaller.
Step 3 Set MED attributes for routes.
# Apply a routing policy to set an MED value for the route advertised by Router B
to Router A (the default MED value of a route is 0).
[RouterB] route-policy policy10 permit node 10
[RouterB-route-policy] apply cost 100
[RouterB-route-policy] quit
[RouterB] bgp 65009
[RouterB-bgp] peer 200.1.1.2 route-policy policy10 export

# View the routing table of Router A.

[RouterA] display bgp routing-table 9.1.1.0 24

BGP local router ID : 1.1.1.1

Local AS number : 65008
Paths: 2 available, 1 best, 1 select

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BGP routing table entry information of 9.1.1.0/24:

From: 200.1.2.1 (3.3.3.3)
Route Duration: 00h07m45s
Direct Out-interface: GigabitEthernet2/0/0
Original nexthop: 200.1.2.1
Qos information : 0x0
AS-path 65009, origin igp, MED 0, pref-val 0, valid, external, best, select, pre 255
Advertised to such 2 peers:
200.1.1.1
200.1.2.1

BGP routing table entry information of 9.1.1.0/24:

From: 200.1.1.1 (2.2.2.2)
Route Duration: 00h00m08s
Direct Out-interface: GigabitEthernet1/0/0
Original nexthop: 200.1.1.1
Qos information : 0x0
AS-path 65009, origin igp, MED 100, pref-val 0, valid, external, pre 255, not preferred for MED
Not advertised to any peer yet

The preceding command output shows that the MED value of the route with the
next-hop address of 200.1.1.1 (Router B) is 100 and the MED value of the route
with the next-hop address of 200.1.2.1 is 0. The route with the smaller MED value
is selected.

----End

Configuration Files
● Configuration file of Router A
#
sysname Router A
#
interface GigabitEthernet1/0/0
ip address 200.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.2 255.255.255.0
#
bgp 65008
router-id 1.1.1.1
peer 200.1.1.1 as-number 65009
peer 200.1.2.1 as-number 65009
#
ipv4-family unicast
undo synchronization
peer 200.1.1.1 enable
peer 200.1.2.1 enable
#
return

● Configuration file of Router B

#
sysname Router B
#
interface GigabitEthernet1/0/0
ip address 9.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.1.1 255.255.255.0
#
bgp 65009
router-id 2.2.2.2
peer 9.1.1.2 as-number 65009
peer 200.1.1.2 as-number 65008
#
ipv4-family unicast

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undo synchronization
network 9.1.1.0 255.255.255.0
peer 9.1.1.2 enable
peer 200.1.1.2 enable
peer 200.1.1.2 route-policy policy10 export
#
route-policy policy10 permit node 10
apply cost 100
#
return

● Configuration file of Router C

#
sysname Router C
#
interface GigabitEthernet1/0/0
ip address 9.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.1 255.255.255.0
#
bgp 65009
router-id 3.3.3.3
peer 9.1.1.1 as-number 65009
peer 200.1.2.2 as-number 65008
#
ipv4-family unicast
undo synchronization
network 9.1.1.0 255.255.255.0
peer 9.1.1.1 enable
peer 200.1.2.2 enable
#
return

9.20.7 Example for Configuring a BGP Route Reflector

Networking Requirements
As shown in Figure 9-32, seven Routers need to form an IBGP network. Full-mesh
BGP connections have been established between Router B, Router D, and Router E.
Users require that the IBGP network be formed without interrupting full-mesh
BGP connections between Router B, Router D, and Router E and require simplified
device configuration and management.

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Figure 9-32 Networking diagram of configuring a BGP RR

GE3/0/0
9.1.1.1/24
AS 65010
GE1/0/0 GE2/0/0
RouterA
GE1/0/0 GE2/0/0
RouerB GE4/0/0 GE1/0/0 RouterC

0 GE GE4/0/0
3/0
/0/ /0
E2

GE3/0/0
G
Cluster1 Cluster2
GE3/0/0 GE1/0/0
GE1/0/0
GE2/0/0 GE1/0/0
GE2/0/0
RouterD RouterE RouterF RouterG

Table 9-8 The BGP RR parameters

Device Interface IP address

RouterA GE 1/0/0 10.1.1.2/24

GE 2/0/0 10.1.3.2/24

GE 3/0/0 9.1.1.1/24

RouterB GE 1/0/0 10.1.1.1/24

GE 2/0/0 10.1.4.1/24

GE 3/0/0 10.1.5.1/24

GE 4/0/0 10.1.2.1/24

RouterC GE 1/0/0 10.1.2.2/24

GE 2/0/0 10.1.3.1/24

GE 3/0/0 10.1.7.1/24

GE 4/0/0 10.1.8.1/24

RouterD GE 1/0/0 10.1.4.2/24

GE 2/0/0 10.1.6.1/24

RouterE GE 2/0/0 10.1.6.2/24

GE 3/0/0 10.1.5.2/24

RouterF GE 1/0/0 10.1.7.2/24

RouterG GE 1/0/0 10.1.8.2/24

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Configuration Roadmap
The configuration roadmap is as follows:
1. Configure RouterB as the route reflector of Cluster1 and RouterD and RouterE
as the clients of RouterB. Prohibit communication between the clients to form
an IBGP network without interrupting full-mesh BGP connections between
RouterB, RouterD, and RouterE.
2. Configure RouterC as the route reflector of Cluster2 and RouterF and
RouterG, as the clients of RouterC to simplify device configuration and
management.

Procedure
Step 1 Configure an IP address for each interface. The configuration details are not
mentioned here.
Step 2 Configure the IBGP connections between the clients and the RR and between the
non-clients and the RR. The configuration details are not mentioned here.
Step 3 Configure the RR.
# Configure Router B.
<Huawei> system-view
[Huawei] sysname RouterB
[RouterB] bgp 65010
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] group in_rr internal
[RouterB-bgp] peer 10.1.4.2 group in_rr
[RouterB-bgp] peer 10.1.5.2 group in_rr
[RouterB-bgp] ipv4-family unicast
[RouterB-bgp-af-ipv4] peer in_rr reflect-client
[RouterB-bgp-af-ipv4] undo reflect between-clients
[RouterB-bgp-af-ipv4] reflector cluster-id 1
[RouterB-bgp-af-ipv4] quit

# Configure Router C.
[RouterC] bgp 65010
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] group in_rr internal
[RouterC-bgp] peer 10.1.7.2 group in_rr
[RouterC-bgp] peer 10.1.8.2 group in_rr
[RouterC-bgp] ipv4-family unicast
[RouterC-bgp-af-ipv4] peer in_rr reflect-client
[RouterC-bgp-af-ipv4] reflector cluster-id 2
[RouterC-bgp-af-ipv4] quit

# Display the routing table of Router D.

[RouterD] display bgp routing-table 9.1.1.0
BGP local router ID : 4.4.4.4
Local AS number : 65010
Paths: 1 available, 0 best, 0 select
BGP routing table entry information of 9.1.1.0/24:
From: 10.1.4.1 (2.2.2.2)
Route Duration: 00h00m14s
Relay IP Nexthop: 0.0.0.0
Relay IP Out-Interface:
Original nexthop: 10.1.1.2

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Qos information : 0x0

AS-path Nil, origin igp, MED 0, localpref 100, pref-val 0, internal, pre 255
Originator: 1.1.1.1
Cluster list: 0.0.0.1
Not advertised to any peer yet

You can view that Router D has learned the route advertised by Router A from
Router B. For details, see the Originator and Cluster_ID attributes of the route.

----End

Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
interface GigabitEthernet1/0/0
ip address 10.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 10.1.3.2 255.255.255.0
#
interface GigabitEthernet3/0/0
ip address 9.1.1.1 255.255.255.0
#
bgp 65010
router-id 1.1.1.1
peer 10.1.1.1 as-number 65010
peer 10.1.3.1 as-number 65010
#
ipv4-family unicast
undo synchronization
network 9.1.1.0 255.255.255.0
peer 10.1.1.1 enable
peer 10.1.3.1 enable
#
return
● Configuration file of Router B
#
sysname RouterB
#
interface GigabitEthernet1/0/0
ip address 10.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 10.1.4.1 255.255.255.0
#
interface GigabitEthernet3/0/0
ip address 10.1.5.1 255.255.255.0
#
interface GigabitEthernet4/0/0
ip address 10.1.2.1 255.255.255.0
#
bgp 65010
router-id 2.2.2.2
peer 10.1.1.2 as-number 65010
peer 10.1.2.2 as-number 65010
group in_rr internal
peer 10.1.4.2 as-number 65010
peer 10.1.4.2 group in_rr
peer 10.1.5.2 as-number 65010
peer 10.1.5.2 group in_rr
#
ipv4-family unicast
undo synchronization
undo reflect between-clients

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reflector cluster-id 1
peer 10.1.1.2 enable
peer 10.1.2.2 enable
peer in_rr enable
peer in_rr reflect-client
peer 10.1.4.2 enable
peer 10.1.4.2 group in_rr
peer 10.1.5.2 enable
peer 10.1.5.2 group in_rr
#
return
● Configuration file of Router C
#
sysname RouterC
#
interface GigabitEthernet1/0/0
ip address 10.1.2.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 10.1.3.1 255.255.255.0
#
interface GigabitEthernet3/0/0
ip address 10.1.7.1 255.255.255.0
#
interface GigabitEthernet4/0/0
ip address 10.1.8.1 255.255.255.0
#
bgp 65010
router-id 3.3.3.3
peer 10.1.2.1 as-number 65010
peer 10.1.3.2 as-number 65010
group in_rr internal
peer 10.1.7.2 as-number 65010
peer 10.1.7.2 group in_rr
peer 10.1.8.2 as-number 65010
peer 10.1.8.2 group in_rr
#
ipv4-family unicast
undo synchronization
reflector cluster-id 2
peer 10.1.2.1 enable
peer 10.1.3.2 enable
peer in_rr enable
peer in_rr reflect-client
peer 10.1.7.2 enable
peer 10.1.7.2 group in_rr
peer 10.1.8.2 enable
peer 10.1.8.2 group in_rr
#
return
● Configuration file of Router D
#
sysname RouterD
#
interface GigabitEthernet1/0/0
ip address 10.1.4.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 10.1.6.1 255.255.255.0
#
bgp 65010
router-id 4.4.4.4
peer 10.1.4.1 as-number 65010
peer 10.1.6.2 as-number 65010
#
ipv4-family unicast
undo synchronization
peer 10.1.4.1 enable

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peer 10.1.6.2 enable

#
return

NOTE

The configuration file of other routers is similar to that of Router D and is omitted here.

9.20.8 Example for Configuring a BGP4+ Route Reflection

Networking Requirements
As shown in Figure 9-33, four devices belong to two ASs. You are required to
perform simplified configuration to ensure that the two ASs communicate with
each other.

Figure 9-33 Networking diagram of configuring BGP4+ route reflection

RouterC AS200
GE2/0/0 GE1/0/0
101::1/96 102::1/96
AS100
GE1/0/0
GE2/0/0 GE1/0/0
101::2/96
100::1/96 102::2/96
GE1/0/0
1::1/64 GE2/0/0
RouterA 100::2/96 RouterB RouterD

Configuration Roadmap
The configuration roadmap is as follows:

1. Configure basic BGP4+ functions to allow BGP neighbors to communicate.

2. Configure RouterC as a route reflector so that no IBGP connection needs to be
established between RouterB and RouterD. This simplifies the configuration.

Procedure
Step 1 Configure an IP address for each interface.

# Configure IPv6 addresses for interfaces on RouterA.

<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] ipv6
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ipv6 enable
[RouterA-GigabitEthernet1/0/0] ipv6 address 1::1/64
[RouterA-GigabitEthernet1/0/0] quit
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet2/0/0] ipv6 enable
[RouterA-GigabitEthernet2/0/0] ipv6 address 100::1/96

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The configurations of RouterB, RouterC and RouterD are similar to the

configuration of RouterA, and are not mentioned here.
Step 2 Configure basic BGP4+ functions.
# Configure RouterA.
[RouterA] ipv6
[RouterA] bgp 100
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 100::2 as-number 200
[RouterA-bgp] ipv6-family unicast
[RouterA-bgp-af-ipv6] peer 100::2 enable
[RouterA-bgp-af-ipv6] network 1:: 64
[RouterA-bgp-af-ipv6] network 100:: 96
[RouterA-bgp-af-ipv6] quit
[RouterA-bgp] quit

# Configure RouterB.
[RouterB] ipv6
[RouterB] bgp 200
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 100::1 as-number 100
[RouterB-bgp] peer 101::1 as-number 200
[RouterB-bgp] ipv6-family unicast
[RouterB-bgp-af-ipv6] peer 100::1 enable
[RouterB-bgp-af-ipv6] peer 101::1 enable
[RouterB-bgp-af-ipv6] network 100:: 96
[RouterB-bgp-af-ipv6] network 101:: 96
[RouterB-bgp-af-ipv6] quit
[RouterB-bgp] quit

# Configure RouterC.
[RouterC] ipv6
[RouterC] bgp 200
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 101::2 as-number 200
[RouterC-bgp] peer 102::2 as-number 200
[RouterC-bgp] ipv6-family unicast
[RouterC-bgp-af-ipv6] peer 101::2 enable
[RouterC-bgp-af-ipv6] peer 102::2 enable
[RouterC-bgp-af-ipv6] network 101:: 96
[RouterC-bgp-af-ipv6] network 102:: 96

# Configure RouterD.
[RouterD] ipv6
[RouterD] bgp 200
[RouterD-bgp] router-id 4.4.4.4
[RouterD-bgp] peer 102::1 as-number 200
[RouterD-bgp] ipv6-family unicast
[RouterD-bgp-af-ipv6] peer 102::1 enable
[RouterD-bgp-af-ipv6] network 102:: 96
[RouterD-bgp-af-ipv6] quit
[RouterD-bgp] quit

Step 3 Configure the route reflector.

# Configure RouterC as a route reflector, and RouterB and RouterD serve as its
clients.
[RouterC-bgp-af-ipv6] peer 101::2 reflect-client
[RouterC-bgp-af-ipv6] peer 102::2 reflect-client

# Check the routing table of RouterB.

[RouterB] display bgp ipv6 routing-table

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BGP Local router ID is 2.2.2.2

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 6

*> Network : 1:: PrefixLen : 64
NextHop : 100::1 LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : 100 i
*> Network : 100:: PrefixLen : 96
NextHop : :: LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : i
NextHop : 100::1 LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : 100 i
*> Network : 101:: PrefixLen : 96
NextHop : :: LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : i
i
NextHop : 101::1 LocPrf : 100
MED :0 PrefVal : 0
Label :
Path/Ogn : i
*>i Network : 102:: PrefixLen : 96
NextHop : 101::1 LocPrf : 100
MED :0 PrefVal : 0
Label :
Path/Ogn : i

# Check the routing table of RouterD.

[RouterD] display bgp ipv6 routing-table

BGP Local router ID is 4.4.4.4

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 5

*>i Network : 1:: PrefixLen : 64
NextHop : 100::1 LocPrf : 100
MED :0 PrefVal : 0
Label :
Path/Ogn : 100 i
*>i Network : 100:: PrefixLen : 96
NextHop : 101::2 LocPrf : 100
MED :0 PrefVal : 0
Label :
Path/Ogn : i
*>i Network : 101:: PrefixLen : 96
NextHop : 102::1 LocPrf : 100
MED :0 PrefVal : 0
Label :
Path/Ogn : i
*> Network : 102:: PrefixLen : 96
NextHop : :: LocPrf :
MED :0 PrefVal : 0
Label :
Path/Ogn : i
i

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NextHop : 102::1 LocPrf : 100

MED :0 PrefVal : 0
Label :
Path/Ogn : i

The routing table shows that RouterD and RouterB learn the routing information
advertised by RouterA from RouterC.

----End

Configuration Files
● Configuration file of RouterA
#
sysname RouterA
#
ipv6
#
interface GigabitEthernet1/0/0
ipv6 enable
ipv6 address 1::1/64
#
interface GigabitEthernet2/0/0
ipv6 enable
ipv6 address 100::1/96
#
bgp 100
router-id 1.1.1.1
peer 100::2 as-number 200
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 1:: 64
network 100:: 96
peer 100::2 enable
#
return
● Configuration file of RouterB
#
sysname RouterB
#
ipv6
#
interface GigabitEthernet1/0/0
ipv6 enable
ipv6 address 101::2/96
#
interface GigabitEthernet2/0/0
ipv6 enable
ipv6 address 100::2/96
#
bgp 200
router-id 2.2.2.2
peer 100::1 as-number 100
peer 101::1 as-number 200
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 100:: 96
network 101:: 96
peer 100::1 enable

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peer 101::1 enable

#
return

● Configuration file of RouterC

#
sysname RouterC
#
ipv6
#
interface GigabitEthernet1/0/0
ipv6 enable
ipv6 address 102::1/96
#
interface GigabitEthernet2/0/0
ipv6 enable
ipv6 address 101::1/96
#
bgp 200
router-id 3.3.3.3
peer 101::2 as-number 200
peer 102::2 as-number 200
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 101:: 96
network 102:: 96
peer 101::2 enable
peer 101::2 reflect-client
peer 102::2 enable
peer 102::2 reflect-client
#
return

● Configuration file of RouterD

#
sysname RouterD
#
ipv6
#
interface GigabitEthernet1/0/0
ipv6 enable
ipv6 address 102::2/96
#
bgp 200
router-id 4.4.4.4
peer 102::1 as-number 200
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 102:: 96
peer 102::1 enable
#
return

9.20.9 Example for Configuring a BGP Confederation

Networking Requirements
As shown in Figure 9-34, there are multiple BGP routers in AS 200. It is required
that the number of IBGP connections be reduced.

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Figure 9-34 Networking diagram of configuring the confederation

RouterB RouterC
GE1/0/0
AS 65002
10.1.2.2/24
GE1/0/0 AS 65003
10.1.1.2/24

10.1.1.1/24
GE3/0/0

GE2/0/0
10.1.2.1/24
GE2/0/0 AS 65001
9.1.1.1/24 RouterD
GE4/0/0 GE1/0/0
10.1.3.1/24 10.1.3.2/24

G .1. G .1.4
GE1/0/0

E0 4 E .2
RouterF

10
200.1.1.1/24 RouterA

/0 .1/ 1/ /2

.1 /0
/1 24 0/ 4

.5 /0
4
GE1/0/0

/2
.1 E2
10
AS 100

10 G
200.1.1.2/24

0
GE2/0/0
AS 200 10.1.5.2/24
RouterE

Configuration Roadmap
The configuration roadmap is as follows:

1. Configure a BGP confederation on each router in AS 200 to divide AS 200 into

three sub-ASs: AS 65001, AS 65002, and AS 65003. Three routers in AS 65001
establish full-mesh IBGP connections to reduce the number of IBGP
connections.

Procedure
Step 1 Configure an IP address to each interface.

# Configure IP addresses for all interfaces of RouterA.

<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 0/0/1
[RouterA-GigabitEthernet0/0/1] ip address 10.1.4.1 255.255.255.0
[RouterA-GigabitEthernet0/0/1] quit
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 200.1.1.1 255.255.255.0
[RouterA-GigabitEthernet1/0/0] quit
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet2/0/0] ip address 10.1.1.1 255.255.255.0
[RouterA-GigabitEthernet2/0/0] quit
[RouterA] interface gigabitethernet 3/0/0
[RouterA-GigabitEthernet3/0/0] ip address 10.1.2.1 255.255.255.0
[RouterA-GigabitEthernet3/0/0] quit
[RouterA] interface gigabitethernet 4/0/0
[RouterA-GigabitEthernet4/0/0] ip address 10.1.3.1 255.255.255.0
[RouterA-GigabitEthernet4/0/0] quit

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The configurations of RouterB, RouterC, RouterD, RouterE and RouterF are similar
to the configuration of RouterA, and are not mentioned here.
Step 2 Configure the BGP confederation.
# Configure Router A.
[RouterA] bgp 65001
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] confederation id 200
[RouterA-bgp] confederation peer-as 65002 65003
[RouterA-bgp] peer 10.1.1.2 as-number 65002
[RouterA-bgp] peer 10.1.2.2 as-number 65003
[RouterA-bgp] ipv4-family unicast
[RouterA-bgp-af-ipv4] peer 10.1.1.2 next-hop-local
[RouterA-bgp-af-ipv4] peer 10.1.2.2 next-hop-local
[RouterA-bgp-af-ipv4] quit

# Configure Router B.
[RouterB] bgp 65002
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] confederation id 200
[RouterB-bgp] confederation peer-as 65001
[RouterB-bgp] peer 10.1.1.1 as-number 65001
[RouterB-bgp] quit

# Configure Router C.
[RouterC] bgp 65003
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] confederation id 200
[RouterC-bgp] confederation peer-as 65001
[RouterC-bgp] peer 10.1.2.1 as-number 65001
[RouterC-bgp] quit

Step 3 Configure IBGP connections inside AS 65001.

# Configure Router A.
[RouterA] bgp 65001
[RouterA-bgp] peer 10.1.3.2 as-number 65001
[RouterA-bgp] peer 10.1.4.2 as-number 65001
[RouterA-bgp] ipv4-family unicast
[RouterA-bgp-af-ipv4] peer 10.1.3.2 next-hop-local
[RouterA-bgp-af-ipv4] peer 10.1.4.2 next-hop-local
[RouterA-bgp-af-ipv4] quit

# Configure Router D.
[RouterD] bgp 65001
[RouterD-bgp] router-id 4.4.4.4
[RouterD-bgp] confederation id 200
[RouterD-bgp] peer 10.1.3.1 as-number 65001
[RouterD-bgp] peer 10.1.5.2 as-number 65001
[RouterD-bgp] quit

# Configure Router E.
[RouterE] bgp 65001
[RouterE-bgp] router-id 5.5.5.5
[RouterE-bgp] confederation id 200
[RouterE-bgp] peer 10.1.4.1 as-number 65001
[RouterE-bgp] peer 10.1.5.1 as-number 65001
[RouterE-bgp] quit

Step 4 Configure the EBGP connection between AS 100 and AS 200.

# Configure Router A.

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[RouterA] bgp 65001

[RouterA-bgp] peer 200.1.1.2 as-number 100
[RouterA-bgp] quit

# Configure Router F.
[RouterF] bgp 100
[RouterF-bgp] router-id 6.6.6.6
[RouterF-bgp] peer 200.1.1.1 as-number 200
[RouterF-bgp] ipv4-family unicast
[RouterF-bgp-af-ipv4] network 9.1.1.0 255.255.255.0
[RouterF-bgp-af-ipv4] quit

Step 5 Verify the configuration.

# Check the routing table of Router B.
[RouterB] display bgp routing-table
BGP Local router ID is 2.2.2.2
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Total Number of Routes: 1
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 9.1.1.0/24 10.1.1.1 0 100 0 (65001) 100i
[RouterB] display bgp routing-table 9.1.1.0
BGP local router ID : 2.2.2.2
Local AS number : 65002
Paths: 1 available, 1 best, 1 select
BGP routing table entry information of 9.1.1.0/24:
From: 10.1.1.1 (1.1.1.1)
Route Duration: 00h12m29s
Relay IP Nexthop: 0.0.0.0
Relay IP Out-Interface: GigabitEthernet1/0/0
Original nexthop: 10.1.1.1
Qos information : 0x0
AS-path (65001) 100, origin igp, MED 0, localpref 100, pref-val 0, valid, external-confed, best, select,
active, pre 255
Not advertised to any peer yet

# Check the BGP routing table of Router D.

[RouterD] display bgp routing-table
BGP Local router ID is 4.4.4.4
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Total Number of Routes: 1
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 9.1.1.0/24 10.1.3.1 0 100 0 100i
[RouterD] display bgp routing-table 9.1.1.0
BGP local router ID : 4.4.4.4
Local AS number : 65001
Paths: 1 available, 1 best, 1 select
BGP routing table entry information of 9.1.1.0/24:
From: 10.1.3.1 (1.1.1.1)
Route Duration: 00h23m57s
Relay IP Nexthop: 0.0.0.0
Relay IP Out-Interface: GigabitEthernet1/0/0
Original nexthop: 10.1.3.1
Qos information : 0x0
AS-path 100, origin igp, MED 0, localpref 100, pref-val 0, valid, internal-confed, best, select, active, pre 255
Not advertised to any peer yet

----End

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Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
interface GigabitEthernet0/0/1
ip address 10.1.4.1 255.255.255.0
#
interface GigabitEthernet1/0/0
ip address 200.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 10.1.1.1 255.255.255.0
#
interface GigabitEthernet3/0/0
ip address 10.1.2.1 255.255.255.0
#
interface GigabitEthernet4/0/0
ip address 10.1.3.1 255.255.255.0
#
bgp 65001
router-id 1.1.1.1
confederation id 200
confederation peer-as 65002 65003
peer 200.1.1.2 as-number 100
peer 10.1.1.2 as-number 65002
peer 10.1.2.2 as-number 65003
peer 10.1.3.2 as-number 65001
peer 10.1.4.2 as-number 65001
#
ipv4-family unicast
undo synchronization
peer 200.1.1.2 enable
peer 10.1.1.2 enable
peer 10.1.1.2 next-hop-local
peer 10.1.2.2 enable
peer 10.1.2.2 next-hop-local
peer 10.1.3.2 enable
peer 10.1.3.2 next-hop-local
peer 10.1.4.2 enable
peer 10.1.4.2 next-hop-local
#
return

● Configuration file of Router B

#
sysname RouterB
#
interface GigabitEthernet1/0/0
ip address 10.1.1.2 255.255.255.0
#
bgp 65002
router-id 2.2.2.2
confederation id 200
confederation peer-as 65001
peer 10.1.1.1 as-number 65001
#
ipv4-family unicast
undo synchronization
peer 10.1.1.1 enable
#
return

NOTE

The configuration file of Router C is similar to that of Router B, and is not mentioned
here.

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● Configuration file of Router D

#
sysname RouterD
#
interface GigabitEthernet1/0/0
ip address 10.1.3.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 10.1.5.1 255.255.255.0
#
bgp 65001
router-id 4.4.4.4
confederation id 200
peer 10.1.3.1 as-number 65001
peer 10.1.5.2 as-number 65001
#
ipv4-family unicast
undo synchronization
peer 10.1.3.1 enable
peer 10.1.5.2 enable
#
return

NOTE

The configuration file of Router E is similar to that of Router D, and is not mentioned
here.
● Configuration file of Router F
#
sysname RouterF
#
interface GigabitEthernet1/0/0
ip address 200.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 9.1.1.1 255.255.255.0
#
bgp 100
router-id 6.6.6.6
peer 200.1.1.1 as-number 200
#
ipv4-family unicast
undo synchronization
network 9.1.1.0 255.255.255.0
peer 200.1.1.1 enable
#
return

9.20.10 Example for Configuring the BGP Community

Attribute
Networking Requirements
As shown in Figure 9-35, EBGP connections are established between Router B and
Router A, and between Router B and Router C. It is required that AS 20 not
advertise the routes advertised by AS 10 to AS 30.

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Figure 9-35 Networking diagram of configuring the BGP community

GE1/0/0
AS 10 9.1.1.1/24
GE2/0/0
200.1.2.1/24
RouterA

EBGP

GE2/0/0 GE1/0/0
200.1.2.2/24 EBGP 200.1.3.2/24

GE1/0/0
200.1.3.1/24 RouterC
RouterB
AS 20 AS 30

Configuration Roadmap
The configuration roadmap is as follows:
1. Configure a route-policy on RouterA to advertise the No_Export attribute so
that AS 20 does not advertise the routes advertised by AS 10 to AS 30.

Procedure
Step 1 Configure an IP address for each interface.
# Configure IP addresses for all interfaces of RouterA.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 9.1.1.1 255.255.255.0
[RouterA-GigabitEthernet1/0/0] quit
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet2/0/0] ip address 200.1.2.1 255.255.255.0
[RouterA-GigabitEthernet2/0/0] quit

The configurations of RouterB and RouterC are similar to the configuration of

RouterA, and are not mentioned here.
Step 2 Establish EBGP connections.
# Configure Router A.
[RouterA] bgp 10
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 200.1.2.2 as-number 20
[RouterA-bgp] ipv4-family unicast
[RouterA-bgp-af-ipv4] network 9.1.1.0 255.255.255.0
[RouterA-bgp-af-ipv4] quit
[RouterA-bgp] quit

# Configure Router B.
[RouterB] bgp 20
[RouterB-bgp] router-id 2.2.2.2

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[RouterB-bgp] peer 200.1.2.1 as-number 10

[RouterB-bgp] peer 200.1.3.2 as-number 30
[RouterB-bgp] quit

# Configure Router C.
[RouterC] bgp 30
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 200.1.3.1 as-number 20
[RouterC-bgp] quit

# On Router B, view detailed information about route 9.1.1.0/24.

[RouterB] display bgp routing-table 9.1.1.0

BGP local router ID : 2.2.2.2

Local AS number : 20
Paths: 1 available, 1 best, 1 select
BGP routing table entry information of 9.1.1.0/24:
From: 200.1.2.1 (1.1.1.1)
Route Duration: 00h00m42s
Direct Out-interface: GigabitEthernet2/0/0
Original nexthop: 200.1.2.1
Qos information : 0x0
AS-path 10, origin igp, MED 0, pref-val 0, valid, external, best, select, active, pre 255
Advertised to such 2 peers:
200.1.2.1
200.1.3.2

The preceding command output shows that Router B advertises the received BGP
route to Router C in AS 30.
# View the BGP routing table of Router C.
[RouterC] display bgp routing-table

BGP Local router ID is 3.3.3.3

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 9.1.1.0/24 200.1.3.1 0 20 10i

The preceding command output shows that Router C has learned route 9.1.1.0/24
from Router B.
Step 3 Configure a BGP community attribute.
# Configure a routing policy on Router A to prevent BGP routes to be advertised
by Router A to Router B from being advertised to any other AS.
[RouterA] route-policy comm_policy permit node 10
[RouterA-route-policy] apply community no-export
[RouterA-route-policy] quit

# Apply the routing policy.

[RouterA] bgp 10
[RouterA-bgp] ipv4-family unicast
[RouterA-bgp-af-ipv4] peer 200.1.2.2 route-policy comm_policy export
[RouterA-bgp-af-ipv4] peer 200.1.2.2 advertise-community

# On Router B, view detailed information about route 9.1.1.0/24.

[RouterB] display bgp routing-table 9.1.1.0

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BGP local router ID : 2.2.2.2

Local AS number : 20
Paths: 1 available, 1 best, 1 select
BGP routing table entry information of 9.1.1.0/24:
From: 200.1.2.1 (1.1.1.1)
Route Duration: 00h00m09s
Direct Out-interface: GigabitEthernet2/0/0
Original nexthop: 200.1.2.1
Qos information : 0x0
Community:no-export
AS-path 10, origin igp, MED 0, pref-val 0, valid, external, best, select, active, pre 255
Not advertised to any peer yet

The preceding command output shows that route 9.1.1.0/24 carries the configured
community attribute and Router B does not advertise this route to any other AS.

----End

Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
interface GigabitEthernet1/0/0
ip address 9.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.1 255.255.255.0
#
bgp 10
router-id 1.1.1.1
peer 200.1.2.2 as-number 20
#
ipv4-family unicast
undo synchronization
network 9.1.1.0 255.255.255.0
peer 200.1.2.2 enable
peer 200.1.2.2 route-policy comm_policy export
peer 200.1.2.2 advertise-community
#
route-policy comm_policy permit node 10
apply community no-export
#
return
● Configuration file of Router B
#
sysname RouterB
#
interface GigabitEthernet1/0/0
ip address 200.1.3.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.2 255.255.255.0
#
bgp 20
router-id 2.2.2.2
peer 200.1.2.1 as-number 10
peer 200.1.3.2 as-number 30
#
ipv4-family unicast
undo synchronization
peer 200.1.2.1 enable
peer 200.1.3.2 enable
#
return

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● Configuration file of Router C

#
sysname RouterC
#
interface GigabitEthernet1/0/0
ip address 200.1.3.2 255.255.255.0
#
bgp 30
router-id 3.3.3.3
peer 200.1.3.1 as-number 20
#
ipv4-family unicast
undo synchronization
peer 200.1.3.1 enable
#
return

9.20.11 Example for Configuring Prefix-based BGP ORF

Networking Requirements
As shown in Figure 9-36, PE1 and PE2 belong to AS 100. PE2 needs to advertise
only the routes that match the import policy of PE1 without having to maintain
export policies.

Figure 9-36 Networking diagram of configuring prefix-based BGP ORF

AS100
PE1
GE1/0/0
111.1.1.1/24
GE1/0/0
111.1.1.2/24 PE2

Configuration Roadmap
The configuration roadmap is as follows:
1. Configure prefix-based BGP ORF so that PE2 can advertise only the routes
that match the import policy of PE1 without having to maintain export
policies.

Procedure
Step 1 Establish an IPv4 unicast peer relationship between PE1 and PE2.
# Configure PE1.
<Huawei> system-view
[Huawei] sysname PE1
[PE1] interface gigabitethernet 1/0/0
[PE1-GigabitEthernet1/0/0] ip address 111.1.1.1 255.255.255.0
[PE1-GigabitEthernet1/0/0] quit
[PE1] bgp 100
[PE1-bgp] peer 111.1.1.2 as-number 100
[PE1-bgp] quit

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# Configure PE2.
<Huawei> system-view
[Huawei] sysname PE2
[PE2] interface gigabitethernet 1/0/0
[PE2-GigabitEthernet1/0/0] ip address 111.1.1.2 255.255.255.0
[PE2-GigabitEthernet1/0/0] quit
[PE2] bgp 100
[PE2-bgp] peer 111.1.1.1 as-number 100
[PE2-bgp] quit

Step 2 Apply the prefix-based inbound policy on PE1.

# Configure PE1.
[PE1] ip ip-prefix 1 permit 4.4.4.0 24 greater-equal 32
[PE1] bgp 100
[PE1-bgp] peer 111.1.1.2 ip-prefix 1 import
[PE1-bgp] quit

# Configure PE2.
[PE2] ip route-static 3.3.3.3 255.255.255.255 NULL0
[PE2] ip route-static 4.4.4.4 255.255.255.255 NULL0
[PE2] ip route-static 5.5.5.5 255.255.255.255 NULL0
[PE2] bgp 100
[PE2-bgp] import static
[PE1-bgp] quit

# Check the routes sent by PE2 to PE1.

[PE2] display bgp routing peer 111.1.1.1 advertised-routes

BGP Local router ID is 111.1.1.2

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 3

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 3.3.3.3/32 111.1.1.2 0 100 0 ?

*> 4.4.4.4/32 111.1.1.2 0 100 0 ?
*> 5.5.5.5/32 111.1.1.2 0 100 0 ?

# Check the routes received by PE1 from PE2.

[PE1] display bgp routing-table peer 111.1.1.2 received-routes

BGP Local router ID is 111.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

Network NextHop MED LocPrf PrefVal Path/Ogn

*>i 4.4.4.4/32 111.1.1.2 0 100 0 ?

When prefix-based BGP ORF is not enabled, PE2 sends routes 3.3.3.3, 4.4.4.4, and
5.5.5.5 to PE1. Because the prefix-based inbound policy is applied on PE1, PE1
receives only route 4.4.4.4.

Step 3 Enable prefix-based BGP ORF.

# Enable prefix-based BGP ORF on PE1.

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[PE1] bgp 100

[PE1-bgp] peer 111.1.1.2 capability-advertise orf ip-prefix both
[PE1-bgp] quit

# Enable prefix-based BGP ORF on PE2.

[PE2] bgp 100
[PE2-bgp] peer 111.1.1.1 capability-advertise orf ip-prefix both
[PE2-bgp] quit

Step 4 Verify the configuration.

# Check the negotiation of prefix-based BGP ORF.
[PE1] display bgp peer 111.1.1.2 verbose

BGP Peer is 111.1.1.2, remote AS 100

Type: IBGP link
BGP version 4, Remote router ID 111.1.1.2
Update-group ID: 2
BGP current state: Established, Up for 00h01m22s
BGP current event: KATimerExpired
BGP last state: OpenConfirm
BGP Peer Up count: 8
Received total routes: 1
Received active routes total: 1
Received mac routes: 0
Advertised total routes: 0
Port: Local - 54845 Remote - 179
Configured: Connect-retry Time: 32 sec
Configured: Active Hold Time: 180 sec Keepalive Time:60 sec
Received : Active Hold Time: 180 sec
Negotiated: Active Hold Time: 180 sec Keepalive Time:60 sec
Peer optional capabilities:
Peer supports bgp multi-protocol extension
Peer supports bgp route refresh capability
Peer supports bgp outbound route filter capability
Support Address-Prefix: IPv4-UNC address-family, rfc-compatible, both
Peer supports bgp 4-byte-as capability
Address family IPv4 Unicast: advertised and received
Received: Total 5 messages
Update messages 1
Open messages 1
KeepAlive messages 2
Notification messages 0
Refresh messages 1
Sent: Total 4 messages
Update messages 0
Open messages 1
KeepAlive messages 2
Notification messages 0
Refresh messages 1
Authentication type configured: None
Last keepalive received: 2011/09/25 18:48:15
Last keepalive sent : 2011/09/25 18:48:19
Last update received: 2011/09/25 16:11:28
Minimum route advertisement interval is 15 seconds
Optional capabilities:
Route refresh capability has been enabled
Outbound route filter capability has been enabled
Enable Address-Prefix: IPv4-UNC address-family, rfc-compatible, both
4-byte-as capability has been enabled
Peer Preferred Value: 0
Routing policy configured:
No import update filter list
No export update filter list
Import prefix list is: 1
No export prefix list
No import route policy
No export route policy

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No import distribute policy

No export distribute policy

# Check the routes sent by PE2 to PE1.

[PE2] display bgp routing peer 111.1.1.1 advertised-routes

BGP Local router ID is 111.1.1.2

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 4.4.4.4/32 111.1.1.2 0 100 0 ?

# Check the routes received by PE1 from PE2.

[PE1] display bgp routing-table peer 111.1.1.2 received-routes

BGP Local router ID is 111.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

Network NextHop MED LocPrf PrefVal Path/Ogn

*>i 4.4.4.4/32 111.1.1.2 0 100 0 ?

After being enabled with prefix-based BGP ORF, PE2 sends only route 4.4.4.4
matching the inbound policy of PE1.

----End

Configuration Files
● Configuration file of PE1
#
sysname PE1
#
interface GigabitEthernet1/0/0
ip address 111.1.1.1 255.255.255.0
#
bgp 100
peer 111.1.1.2 as-number 100
#
ipv4-family unicast
undo synchronization
peer 111.1.1.2 enable
peer 111.1.1.2 ip-prefix 1 import
peer 111.1.1.2 capability-advertise orf ip-prefix both
#
ip ip-prefix 1 index 10 permit 4.4.4.0 24 greater-equal 32 less-equal 32
#
return
● Configuration file of PE2
#
sysname PE2
#
interface GigabitEthernet1/0/0
ip address 111.1.1.2 255.255.255.0
#
bgp 100

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peer 111.1.1.1 as-number 100

#
ipv4-family unicast
undo synchronization
import-route static
peer 111.1.1.1 enable
peer 111.1.1.1 capability-advertise orf ip-prefix both
#
ip route-static 3.3.3.3 255.255.255.255 NULL0
ip route-static 4.4.4.4 255.255.255.255 NULL0
ip route-static 5.5.5.5 255.255.255.255 NULL0
#
return

9.20.12 Example for Configuring BGP Load Balancing

Networking Requirements
On the network shown in Figure 9-37, BGP is configured on all routers. RouterA is
in AS 100. RouterB and RouterC are in AS 300. RouterD is in AS 200. Network
congestion from RouterA to destination address 8.1.1.0/24 needs to be relieved
and network resources need to be fully utilized.

Figure 9-37 Networking diagram of configuring BGP load balancing

RouterA AS100

GE1/0/0 GE2/0/0
200.1.1.1/24 200.1.2.1/24

GE1/0/0 GE2/0/0
200.1.1.2/24 200.1.2.2/24
RouterB RouterC

GE2/0/0 AS300 GE1/0/0

200.1.3.2/24 200.1.4.2/24

GE2/0/0 GE1/0/0
200.1.3.1/24 200.1.4.1/24
GE3/0/0
AS200 8.1.1.1/24
RouterD

Configuration Roadmap
The configuration roadmap is as follows:

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1. Establish EBGP connections between RouterA and RouterB and between

RouterA and RouterC, between RouterD and RouterB and between RouterD
and RouterC to enable ASs to communicate with each other using BGP.
2. Configuring load balancing on RouterA so that RouterA can send traffic to
RouterD through either RouterB or RouterC.

Procedure
Step 1 Configure an IP address for each interface.
# Configure IP addresses for all interfaces of RouterA.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 200.1.1.1 255.255.255.0
[RouterA-GigabitEthernet1/0/0] quit
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet2/0/0] ip address 200.1.2.1 255.255.255.0
[RouterA-GigabitEthernet2/0/0] quit

The configurations of RouterB, RouterC and RouterD are similar to the

configuration of RouterA, and are not mentioned here.
Step 2 Establish BGP connections.
# Configure RouterA.
[RouterA] bgp 100
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 200.1.1.2 as-number 300
[RouterA-bgp] peer 200.1.2.2 as-number 300
[RouterA-bgp] quit

# Configure RouterB.
[RouterB] bgp 300
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 200.1.1.1 as-number 100
[RouterB-bgp] peer 200.1.3.1 as-number 200
[RouterB-bgp] quit

# Configure RouterC.
[RouterC] bgp 300
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 200.1.2.1 as-number 100
[RouterC-bgp] peer 200.1.4.1 as-number 200
[RouterC-bgp] quit

# Configure RouterD.
[RouterD] bgp 200
[RouterD-bgp] router-id 4.4.4.4
[RouterD-bgp] peer 200.1.3.2 as-number 300
[RouterD-bgp] peer 200.1.4.2 as-number 300
[RouterD-bgp] ipv4-family unicast
[RouterD-bgp-af-ipv4] network 8.1.1.0 255.255.255.0
[RouterD-bgp-af-ipv4] quit
[RouterD-bgp] quit

# View the routing table of RouterA.

[RouterA] display bgp routing-table 8.1.1.0 24

BGP local router ID : 1.1.1.1

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Local AS number : 100

Paths : 2 available, 1 best, 1 select
BGP routing table entry information of 8.1.1.0/24:
From: 200.1.1.2 (2.2.2.2)
Route Duration: 00h00m50s
Direct Out-interface: GigabitEthernet1/0/0
Original nexthop: 200.1.1.2
Qos information : 0x0
AS-path 300 200, origin igp, pref-val 0, valid, external, best, select, active, pre 255
Advertised to such 2 peers:
200.1.1.2
200.1.2.2

BGP routing table entry information of 8.1.1.0/24:

From: 200.1.2.2 (3.3.3.3)
Route Duration: 00h00m51s
Direct Out-interface: GigabitEthernet2/0/0
Original nexthop: 200.1.2.2
Qos information : 0x0
AS-path 300 200, origin igp, pref-val 0, valid, external, pre 255, not preferred for router ID
Not advertised to any peer yet

The preceding command output shows that there are two valid routes from
RouterA to destination 8.1.1.0/24. The route with the next-hop address of
200.1.1.2 is the optimal route because the router ID of RouterB is smaller.
Step 3 Configure BGP load balancing.
# Configure load balancing on RouterA.
[RouterA] bgp 100
[RouterA-bgp] ipv4-family unicast
[RouterA-bgp-af-ipv4] maximum load-balancing 2
[RouterA-bgp-af-ipv4] quit
[RouterA-bgp] quit

Step 4 Verify the configuration.

# View the routing table of RouterA.
[RouterA] display bgp routing-table 8.1.1.0 24

BGP local router ID : 1.1.1.1

Local AS number : 100
Paths : 2 available, 1 best, 2 select
BGP routing table entry information of 8.1.1.0/24:
From: 200.1.1.2 (2.2.2.2)
Route Duration: 00h03m55s
Direct Out-interface: GigabitEthernet1/0/0
Original nexthop: 200.1.1.2
Qos information : 0x0
AS-path 300 200, origin igp, pref-val 0, valid, external, best, select, active, pre 255
Advertised to such 2 peers
200.1.1.2
200.1.2.2

BGP routing table entry information of 8.1.1.0/24:

From: 200.1.2.2 (3.3.3.3)
Route Duration: 00h03m56s
Direct Out-interface: GigabitEthernet2/0/0
Original nexthop: 200.1.2.2
Qos information : 0x0
AS-path 300 200, origin igp, pref-val 0, valid, external, select, active, pre 255, not preferred for router ID
Not advertised to any peer yet

The preceding command output shows that BGP route 8.1.1.0/24 has two next
hops: 200.1.1.2 and 200.1.2.2. Both of them are optimal routes.
----End

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Configuration Files
● Configuration file of RouterA
#
sysname RouterA
#
interface GigabitEthernet1/0/0
ip address 200.1.1.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.1 255.255.255.0
#
interface LoopBack0
ip address 1.1.1.1 255.255.255.255
#
bgp 100
router-id 1.1.1.1
peer 200.1.1.2 as-number 300
peer 200.1.2.2 as-number 300
#
ipv4-family unicast
undo synchronization
maximum load-balancing 2
peer 200.1.1.2 enable
peer 200.1.2.2 enable
#
return
● Configuration file of RouterB
#
sysname RouterB
#
interface GigabitEthernet1/0/0
ip address 200.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.3.2 255.255.255.0
#
interface LoopBack0
ip address 2.2.2.2 255.255.255.255
#
bgp 300
router-id 2.2.2.2
peer 200.1.1.1 as-number 100
peer 200.1.3.1 as-number 200
#
ipv4-family unicast
undo synchronization
peer 200.1.1.1 enable
peer 200.1.3.1 enable
#
return
● Configuration file of RouterC
#
sysname RouterC
#
interface GigabitEthernet1/0/0
ip address 200.1.4.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.2.2 255.255.255.0
#
interface LoopBack0
ip address 3.3.3.3 255.255.255.255
#
bgp 300
router-id 3.3.3.3
peer 200.1.2.1 as-number 100

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peer 200.1.4.1 as-number 200

#
ipv4-family unicast
undo synchronization
peer 200.1.2.1 enable
peer 200.1.4.1 enable
#
return

● Configuration file of RouterD

#
sysname RouterD
#
interface GigabitEthernet1/0/0
ip address 200.1.4.1 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 200.1.3.1 255.255.255.0
#
interface GigabitEthernet3/0/0
ip address 8.1.1.1 255.255.255.0
#
interface LoopBack0
ip address 4.4.4.4 255.255.255.255
#
bgp 200
router-id 4.4.4.4
peer 200.1.3.2 as-number 300
peer 200.1.4.2 as-number 300
#
ipv4-family unicast
undo synchronization
network 8.1.1.0 255.255.255.0
peer 200.1.3.2 enable
peer 200.1.4.2 enable
#
return

9.20.13 Example for Associating BGP with BFD

Networking Requirements
As shown in Figure 9-38, RouterA belongs to AS 100, RouterB and RouterC belong
to AS 200. EBGP connections are established between RouterA and RouterB, and
between RouterA and RouterC.
Service traffic is transmitted along the primary link RouterA->RouterB. The link
RouterA->RouterC->RouterB functions as the backup link. Fast fault detection is
required to allow traffic to be fast switched from the primary link to the backup
link.

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Figure 9-38 Networking diagram of configuring BFD for BGP

GE3/0/0
172.16.1.1/24
GE2/0/0
200.1.1.2/24

GE1/0/0 EBGP GE1/0/0

AS 100 RouterB
200.1.1.1/24 9.1.1.1/24

RouterA IBGP
AS 200
GE2/0/0
200.1.2.1/24 EBGP GE1/0/0
9.1.1.2/24

GE2/0/0
200.1.2.2/24
RouterC

Configuration Roadmap
The configuration roadmap is as follows:
1. Configure basic BGP functions on each router.
2. Configure the MED attribute to control route selection.
3. Enable BFD on RouterA and RouterB.
NOTE

If two routers establish an EBGP peer relationship over a direct link, BFD for BGP does not
need to be configured. This is because the ebgp-interface-sensitive command is enabled
by default for directly-connected EBGP peers.

Procedure
Step 1 Configure an IP address for each interface.
# Configure IP addresses for all interfaces of RouterA.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 200.1.1.1 255.255.255.0
[RouterA-GigabitEthernet1/0/0] quit
[RouterA] interface gigabitethernet 2/0/0
[RouterA-GigabitEthernet2/0/0] ip address 200.1.2.1 255.255.255.0
[RouterA-GigabitEthernet2/0/0] quit

The configurations of RouterB and RouterC are similar to the configuration of

RouterA, and are not mentioned here.
Step 2 Configure basic BGP functions. Establish EBGP peer relationships between RouterA
and RouterB, and between RouterA and RouterC and an IBGP peer relationship
between RouterB and RouterC.
# Configure RouterA.

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[RouterA] bgp 100

[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 200.1.1.2 as-number 200
[RouterA-bgp] peer 200.1.1.2 ebgp-max-hop
[RouterA-bgp] peer 200.1.2.2 as-number 200
[RouterA-bgp] peer 200.1.2.2 ebgp-max-hop
[RouterA-bgp] quit

# Configure RouterB.
[RouterB] bgp 200
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 200.1.1.1 as-number 100
[RouterB-bgp] peer 200.1.1.1 ebgp-max-hop
[RouterB-bgp] peer 9.1.1.2 as-number 200
[RouterB-bgp] network 172.16.1.0 255.255.255.0
[RouterB-bgp] quit

# Configure RouterC.
[RouterC] bgp 200
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 200.1.2.1 as-number 100
[RouterC-bgp] peer 200.1.2.1 ebgp-max-hop
[RouterC-bgp] peer 9.1.1.1 as-number 200
[RouterC-bgp] quit

# Check the status of BGP peer relationships on RouterA. The command output
shows that the BGP peer relationships are in the Established state.
<RouterA> display bgp peer

BGP local router ID : 1.1.1.1

Local AS number : 100
Total number of peers : 2 Peers in established state : 2

Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv

200.1.1.2 4 200 2 5 0 00:01:25 Established 0

200.1.2.2 4 200 2 4 0 00:00:55 Established 0

Step 3 Configure the MED attribute.

Set the MED value for the route sent from RouterC or RouterB to RouterA by
using a routing policy.
# Configure RouterB.
[RouterB] route-policy 10 permit node 10
[RouterB-route-policy] apply cost 100
[RouterB-route-policy] quit
[RouterB] bgp 200
[RouterB-bgp] peer 200.1.1.1 route-policy 10 export

# Configure RouterC.
[RouterC] route-policy 10 permit node 10
[RouterC-route-policy] apply cost 150
[RouterC-route-policy] quit
[RouterC] bgp 200
[RouterC-bgp] peer 200.1.2.1 route-policy 10 export

# Check BGP routing information on RouterA.

<RouterA> display bgp routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale

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Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 5

Network NextHop MED LocPrf PrefVal Path/Ogn
*> 9.1.1.0/24 200.1.2.2 150 0 200?
*> 172.16.1.0/24 200.1.1.2 100 0 200i
* 200.1.2.2 150 0 200i
*> 200.1.2.0 200.1.1.2 100 0 200?
200.1.2.2 150 0 200?

As shown in the BGP routing table, the next-hop address of the route to
172.16.1.0/24 is 200.1.1.2, and service traffic is transmitted on the primary link
between RouterA and RouterB.
Step 4 Configure BFD, and set the interval for transmitting BFD packets, the interval for
receiving BFD packets, and the local detection multiplier.
# Enable BFD on RouterA. Set the minimum intervals for transmitting and
receiving BFD packets to 100 ms and the local detection multiplier to 4.
[RouterA] bfd
[RouterA-bfd] quit
[RouterA] bgp 100
[RouterA-bgp] peer 200.1.1.2 bfd enable
[RouterA-bgp] peer 200.1.1.2 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4

# Enable BFD on RouterB. Set the minimum intervals for transmitting and
receiving BFD packets to 100 ms and the local detection multiplier to 4.
[RouterB] bfd
[RouterB-bfd] quit
[RouterB] bgp 200
[RouterB-bgp] peer 200.1.1.1 bfd enable
[RouterB-bgp] peer 200.1.1.1 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4

# Display all BFD sessions on RouterA.

<RouterA> display bgp bfd session all
Local_Address Peer_Address LD/RD Interface
200.1.1.1 200.1.1.2 8201/8201 GigibitEthernet1/0/0
Tx-interval(ms) Rx-interval(ms) Multiplier Session-State
100 100 4 Up
Wtr-interval(m)
0

Step 5 Verify the configuration.

# Run the shutdown command on GE 2/0/0 of RouterB to simulate a fault on the
primary link.
[RouterB] interface gigabitethernet 2/0/0
[RouterB-Gigabitethernet2/0/0] shutdown

# Check the BGP routing table on RouterA.

<RouterA> display bgp routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 3

Network NextHop MED LocPrf PrefVal Path/Ogn

*> 9.1.1.0/24 200.1.2.2 150 0 200?

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*> 172.16.1.0/24 200.1.2.2 150 0 200i

200.1.2.0 200.1.2.2 150 0 200?

As shown in the BGP routing table, the backup link of RouterA -> RouterC ->
RouterB takes effect after the primary link fails, and the next-hop address of the
route to 172.16.1.0/24 is 200.1.2.2.

----End

Configuration Files
● Configuration file of RouterA
#
sysname RouterA
#
bfd
#
interface Gigabitethernet1/0/0
ip address 200.1.1.1 255.255.255.0
#
interface Gigabitethernet2/0/0
ip address 200.1.2.1 255.255.255.0
#
bgp 100
router-id 1.1.1.1
peer 200.1.1.2 as-number 200
peer 200.1.1.2 ebgp-max-hop 255
peer 200.1.1.2 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4
peer 200.1.1.2 bfd enable
peer 200.1.2.2 as-number 200
peer 200.1.2.2 ebgp-max-hop 255
#
ipv4-family unicast
undo synchronization
peer 200.1.1.2 enable
peer 200.1.2.2 enable
#
return

● Configuration file of RouterB

#
sysname RouterB
#
bfd
#
interface Gigabitethernet1/0/0
ip address 9.1.1.1 255.255.255.0
#
interface Gigabitethernet2/0/0
ip address 200.1.1.2 255.255.255.0
#
interface Gigabitethernet3/0/0
ip address 172.16.1.1 255.255.255.0
#
bgp 200
router-id 2.2.2.2
peer 9.1.1.2 as-number 200
peer 200.1.1.1 as-number 100
peer 200.1.1.1 ebgp-max-hop 255
peer 200.1.1.1 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4
peer 200.1.1.1 bfd enable
#
ipv4-family unicast
undo synchronization
network 172.16.1.0 255.255.255.0
peer 9.1.1.2 enable
peer 200.1.1.1 enable

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peer 200.1.1.1 route-policy 10 export

#
route-policy 10 permit node 10
apply cost 100
#
return

● Configuration file of RouterC

#
sysname RouterC
#
bfd
#
interface Gigabitethernet1/0/0
ip address 9.1.1.2 255.255.255.0
#
interface Gigabitethernet2/0/0
ip address 200.1.2.2 255.255.255.0
#
bgp 200
router-id 3.3.3.3
peer 9.1.1.1 as-number 200
peer 200.1.2.1 as-number 100
peer 200.1.2.1 ebgp-max-hop 255
#
ipv4-family unicast
undo synchronization
import-route direct
peer 9.1.1.1 enable
peer 200.1.2.1 enable
peer 200.1.2.1 route-policy 10 export
#
route-policy 10 permit node 10
apply cost 150
#
return

9.20.14 Example for Configuring BGP GTSM

Networking Requirements
As shown in Figure 9-39, Router A belongs to AS 10, and Router B, Router C, and
Router D belong to AS 20. BGP is run in the network and it is required to protect
Router B against CPU-utilization attacks.

Figure 9-39 Figure 1 Networking diagram of configuring BGP GTSM

IBGP
GE1/0/0 RouterB GE2/0/0 GE1/0/0 RouterC
EBGP 10.1.1.2/24 20.1.1.1/24 20.1.1.2/24
GE2/0/0
RouterA 20.1.2.1/24
Lo .3.3

Loopback0 IBGP
op .9

GE1/0/0
3

ba /32

10.1.1.1/24 2.2.2.9/32 IB
GP GE1/0/0
ck

AS10
0

20.1.2.2/24

RouterD
PC
AS20
Loopback0
4.4.4.9/32

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Configuration Roadmap
The configuration roadmap is as follows:
1. Configure OSPF on Router B, Router C, and Router D to implement
interworking in AS 20.
2. Set up an EBGP connection between Router A and Router B, and set up IBGP
connections between Router B, Router C, and Router D through loopback
interfaces.
3. Configure GTSM on Router A, Router B, Router C, and Router D so that it can
protect Router B against CPU-utilization attacks.

Procedure
Step 1 Configure an IP address to each interface.
# Configure IP addresses for all interfaces of RouterA.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 10.1.1.1 255.255.255.0
[RouterA-GigabitEthernet1/0/0] quit

The configurations of RouterB, RouterC and RouterD are similar to the

configuration of RouterA, and are not mentioned here.
Step 2 Configure OSPF.
# Configure RouterB.
[RouterB] ospf
[RouterB-ospf-1] area 0
[RouterB-ospf-1-area-0.0.0.0] network 20.1.1.0 0.0.0.255
[RouterB-ospf-1-area-0.0.0.0] quit
[RouterB-ospf-1] area 1
[RouterB-ospf-1-area-0.0.0.1] network 2.2.2.9 0.0.0.0
[RouterB-ospf-1-area-0.0.0.1] quit
[RouterB-ospf-1] quit

# Configure RouterC.
[RouterC] ospf
[RouterC-ospf-1] area 0
[RouterC-ospf-1-area-0.0.0.0] network 20.1.2.0 0.0.0.255
[RouterC-ospf-1-area-0.0.0.0] quit
[RouterC-ospf-1] area 1
[RouterC-ospf-1-area-0.0.0.1] network 20.1.1.0 0.0.0.255
[RouterC-ospf-1-area-0.0.0.1] quit
[RouterC-ospf-1] area 2
[RouterC-ospf-1-area-0.0.0.1] network 3.3.3.9 0.0.0.0
[RouterC-ospf-1-area-0.0.0.1] quit
[RouterC-ospf-1] quit

# Configure RouterD.
[RouterD] ospf
[RouterD-ospf-1] area 0
[RouterD-ospf-1-area-0.0.0.0] network 20.1.2.0 0.0.0.255
[RouterD-ospf-1-area-0.0.0.0] quit
[RouterD-ospf-1] area 1
[RouterD-ospf-1-area-0.0.0.1] network 4.4.4.9 0.0.0.0
[RouterD-ospf-1-area-0.0.0.1] quit
[RouterD-ospf-1] quit

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Step 3 Configure an IBGP connection.

# Configure Router B.
[RouterB] bgp 20
[RouterB-bgp] router-id 2.2.2.9
[RouterB-bgp] peer 3.3.3.9 as-number 20
[RouterB-bgp] peer 3.3.3.9 connect-interface LoopBack0
[RouterB-bgp] peer 3.3.3.9 next-hop-local
[RouterB-bgp] peer 4.4.4.9 as-number 20
[RouterB-bgp] peer 4.4.4.9 connect-interface LoopBack0
[RouterB-bgp] peer 4.4.4.9 next-hop-local

# Configure Router C.
[RouterC] bgp 20
[RouterC-bgp] router-id 3.3.3.9
[RouterC-bgp] peer 2.2.2.9 as-number 20
[RouterC-bgp] peer 2.2.2.9 connect-interface LoopBack0
[RouterC-bgp] peer 4.4.4.9 as-number 20
[RouterC-bgp] peer 4.4.4.9 connect-interface LoopBack0

# Configure Router D.
[RouterD] bgp 20
[RouterD-bgp] router-id 4.4.4.9
[RouterD-bgp] peer 2.2.2.9 as-number 20
[RouterD-bgp] peer 2.2.2.9 connect-interface LoopBack0
[RouterD-bgp] peer 3.3.3.9 as-number 20
[RouterD-bgp] peer 3.3.3.9 connect-interface LoopBack0

Step 4 Configure an EBGP connection.

# Configure Router A.
[RouterA] bgp 10
[RouterA-bgp] router-id 1.1.1.9
[RouterA-bgp] peer 10.1.1.2 as-number 20

# Configure Router B.
[RouterB-bgp] peer 10.1.1.1 as-number 10

# Display the connection status of the BGP peers.

[RouterB-bgp] display bgp peer
BGP local router ID : 2.2.2.9
Local AS number : 20
Total number of peers : 3 Peers in established state : 3

Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv

3.3.3.9 4 20 8 7 0 00:05:06 Established 0

4.4.4.9 4 20 8 10 0 00:05:33 Established 0
10.1.1.1 4 10 7 7 0 00:04:09 Established 0

You can view that Router B has set up BGP connections with other routers.
Step 5 Configure GTSM on Router A and Router B. Router A and Router B are directly
connected, so the range of the TTL value between the two routers is [255, 255].
The value of valid-ttl-hops is 1.
# Configure GTSM on Router A.
[RouterA-bgp] peer 10.1.1.2 valid-ttl-hops 1

# Configure GTSM of the EBGP connection on Router B.

[RouterB-bgp] peer 10.1.1.1 valid-ttl-hops 1

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# Check the GTSM configuration.

[RouterB-bgp] display bgp peer 10.1.1.1 verbose
BGP Peer is 10.1.1.1, remote AS 10
Type: EBGP link
BGP version 4, Remote router ID 1.1.1.9

Update-group ID : 2
BGP current state: Established, Up for 00h49m35s
BGP current event: RecvKeepalive
BGP last state: OpenConfirm
BGP Peer Up count: 1
Received total routes: 0
Received active routes total: 0
Received mac routes: 0
Advertised total routes: 0
Port: Local - 179 Remote - 52876
Configured: Connect-retry Time: 32 sec
Configured: Active Hold Time: 180 sec Keepalive Time:60 sec
Received : Active Hold Time: 180 sec
Negotiated: Active Hold Time: 180 sec Keepalive Time:60 sec
Peer optional capabilities:
Peer supports bgp multi-protocol extension
Peer supports bgp route refresh capability
Peer supports bgp 4-byte-as capability
Address family IPv4 Unicast: advertised and received
Received: Total 59 messages
Update messages 0
Open messages 2
KeepAlive messages 57
Notification messages 0
Refresh messages 0
Sent: Total 79 messages
Update messages 5
Open messages 2
KeepAlive messages 71
Notification messages 1
Refresh messages 0
Authentication type configured: None
Last keepalive received: 2011/09/25 16:41:19
Last keepalive sent : 2011/09/25 16:41:22
Last update received: 2011/09/25 16:11:28
Last update sent : 2011/09/25 16:11:32
Minimum route advertisement interval is 30 seconds
Optional capabilities:
Route refresh capability has been enabled
4-byte-as capability has been enabled
GTSM has been enabled, valid-ttl-hops: 1
Peer Preferred Value: 0
Routing policy configured:
No routing policy is configured

You can view that GTSM is enabled, the valid hop count is 1, and the BGP
connection is in the Established state.

Step 6 Configure GTSM on Router B and Router C. Router B and Router C are directly
connected, so the range of the TTL value between the two routers is [255, 255].
The value of valid-ttl-hops is 1.

# Configure GTSM on Router B.

[RouterB-bgp] peer 3.3.3.9 valid-ttl-hops 1

# Configure GTSM of the IBGP connection on Router C.

[RouterC-bgp] peer 2.2.2.9 valid-ttl-hops 1

# View the GTSM configuration.

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[RouterB-bgp] display bgp peer 3.3.3.9 verbose

BGP Peer is 3.3.3.9, remote AS 20
Type: IBGP link
BGP version 4, Remote router ID 3.3.3.9

Update-group ID : 0
BGP current state: Established, Up for 00h54m36s
BGP current event: KATimerExpired
BGP last state: OpenConfirm
BGP Peer Up count: 1
Received total routes: 0
Received active routes total: 0
Received mac routes: 0
Advertised total routes: 0
Port: Local - 54998 Remote - 179
Configured: Connect-retry Time: 32 sec
Configured: Active Hold Time: 180 sec Keepalive Time:60 sec
Received : Active Hold Time: 180 sec
Negotiated: Active Hold Time: 180 sec Keepalive Time:60 sec
Peer optional capabilities:
Peer supports bgp multi-protocol extension
Peer supports bgp route refresh capability
Peer supports bgp 4-byte-as capability
Address family IPv4 Unicast: advertised and received
Received: Total 63 messages
Update messages 0
Open messages 1
KeepAlive messages 62
Notification messages 0
Refresh messages 0
Sent: Total 69 messages
Update messages 10
Open messages 1
KeepAlive messages 58
Notification messages 0
Refresh messages 0
Authentication type configured: None
Last keepalive received: 2011/09/25 16:46:19
Last keepalive sent : 2011/09/25 16:46:21
Last update received: 2011/09/25 16:11:28
Last update sent : 2011/09/25 16:11:32
Minimum route advertisement interval is 15 seconds
Optional capabilities:
Route refresh capability has been enabled
4-byte-as capability has been enabled
Nexthop self has been configured
Connect-interface has been configured
GTSM has been enabled, valid-ttl-hops: 1
Peer Preferred Value: 0
Routing policy configured:
No routing policy is configured

You can view that GTSM is enabled, the valid hop count is 1, and the BGP
connection is in the Established state.

Step 7 Configure GTSM on Router C and Router D. Router C and Router D are directly
connected, so the range of the TTL value between the two routers is [255, 255].
The value of valid-ttl-hops is 1.

# Configure GTSM of the IBGP connection on Router C.

[RouterC-bgp] peer 4.4.4.9 valid-ttl-hops 1

# Configure GTSM of the IBGP connection on Router D.

[RouterD-bgp] peer 3.3.3.9 valid-ttl-hops 1

# Check the GTSM configuration.

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[RouterC-bgp] display bgp peer 4.4.4.9 verbose

BGP Peer is 4.4.4.9, remote AS 20
Type: IBGP link
BGP version 4, Remote router ID 4.4.4.9

Update-group ID : 1
BGP current state: Established, Up for 00h56m06s
BGP current event: KATimerExpired
BGP last state: OpenConfirm
BGP Peer Up count: 1
Received total routes: 0
Received active routes total: 0
Received mac routes: 0
Advertised total routes: 0
Port: Local - 179 Remote - 53758
Configured: Connect-retry Time: 32 sec
Configured: Active Hold Time: 180 sec Keepalive Time:60 sec
Received : Active Hold Time: 180 sec
Negotiated: Active Hold Time: 180 sec Keepalive Time:60 sec
Peer optional capabilities:
Peer supports bgp multi-protocol extension
Peer supports bgp route refresh capability
Peer supports bgp 4-byte-as capability
Address family IPv4 Unicast: advertised and received
Received: Total 63 messages
Update messages 0
Open messages 1
KeepAlive messages 62
Notification messages 0
Refresh messages 0
Sent: Total 63 messages
Update messages 0
Open messages 2
KeepAlive messages 61
Notification messages 0
Refresh messages 0
Authentication type configured: None
Last keepalive received: 2011/09/25 16:47:19
Last keepalive sent : 2011/09/25 16:47:21
Last update received: 2011/09/25 16:11:28
Last update sent : 2011/09/25 16:11:32
Minimum route advertisement interval is 15 seconds
Optional capabilities:
Route refresh capability has been enabled
4-byte-as capability has been enabled
Connect-interface has been configured
GTSM has been enabled, valid-ttl-hops: 1
Peer Preferred Value: 0
Routing policy configured:
No routing policy is configured

You can view that GTSM is enabled, the valid hop count is 1, and the BGP
connection is in the Established state.
Step 8 Configure GTSM on Router B and Router D. Router B and Router D are connected
by Router C, so the range of the TTL value between the two routers is [254, 255].
The value of valid-ttl-hops is 2.
# Configure GTSM of the IBGP connection on Router B.
[RouterB-bgp] peer 4.4.4.9 valid-ttl-hops 2

# Configure GTSM on Router D.

[RouterD-bgp] peer 2.2.2.9 valid-ttl-hops 2

# Check the GTSM configuration.

[RouterB-bgp] display bgp peer 4.4.4.9 verbose

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BGP Peer is 4.4.4.9, remote AS 20

Type: IBGP link
BGP version 4, Remote router ID 4.4.4.9

Update-group ID : 0
BGP current state: Established, Up for 00h57m48s
BGP current event: RecvKeepalive
BGP last state: OpenConfirm
BGP Peer Up count: 1
Received total routes: 0
Received active routes total: 0
Received mac routes: 0
Advertised total routes: 0
Port: Local - 53714 Remote - 179
Configured: Connect-retry Time: 32 sec
Configured: Active Hold Time: 180 sec Keepalive Time:60 sec
Received : Active Hold Time: 180 sec
Negotiated: Active Hold Time: 180 sec Keepalive Time:60 sec
Peer optional capabilities:
Peer supports bgp multi-protocol extension
Peer supports bgp route refresh capability
Peer supports bgp 4-byte-as capability
Address family IPv4 Unicast: advertised and received
Received: Total 72 messages
Update messages 0
Open messages 1
KeepAlive messages 71
Notification messages 0
Refresh messages 0
Sent: Total 82 messages
Update messages 10
Open messages 1
KeepAlive messages 71
Notification messages 0
Refresh messages 0
Authentication type configured: None
Last keepalive received: 2011/09/25 16:47:19
Last keepalive sent : 2011/09/25 16:47:21
Last update received: 2011/09/25 16:11:28
Last update sent : 2011/09/25 16:11:32
Minimum route advertisement interval is 15 seconds
Optional capabilities:
Route refresh capability has been enabled
4-byte-as capability has been enabled
Nexthop self has been configured
Connect-interface has been configured
GTSM has been enabled, valid-ttl-hops: 2
Peer Preferred Value: 0
Routing policy configured:
No routing policy is configured

You can view that GTSM is configured, the valid hop count is 2, and the BGP
connection is in the Established state.

NOTE

● In this example, if the value of valid-ttl-hops of either Router B or Router D is smaller

than 2, the IBGP connection cannot be set up.
● GTSM must be configured on the two ends of the BGP connection.

Step 9 Verify the configuration.

# Run the display gtsm statistics all command on Router B to check the GTSM
statistics of Router B. By default, Router B does not discard any packet when all
packets match the GTSM policy.
[RouterB-bgp] display gtsm statistics all

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GTSM Statistics Table

----------------------------------------------------------------
SlotId Protocol Total Counters Drop Counters Pass Counters
----------------------------------------------------------------
0 BGP 17 0 17
0 BGPv6 0 0 0
0 OSPF 0 0 0
0 LDP 0 0 0
1 BGP 0 0 0
1 BGPv6 0 0 0
1 OSPF 0 0 0
1 LDP 0 0 0
2 BGP 0 0 0
2 BGPv6 0 0 0
2 OSPF 0 0 0
2 LDP 0 0 0
3 BGP 0 0 0
3 BGPv6 0 0 0
3 OSPF 0 0 0
3 LDP 0 0 0
4 BGP 32 0 32
4 BGPv6 0 0 0
4 OSPF 0 0 0
4 LDP 0 0 0
5 BGP 0 0 0
5 BGPv6 0 0 0
5 OSPF 0 0 0
5 LDP 0 0 0
7 BGP 0 0 0
7 BGPv6 0 0 0
7 OSPF 0 0 0
7 LDP 0 0 0
----------------------------------------------------------------

If the host simulates the BGP packets of Router A to attack Router B, the packets
are discarded because their TTL value is not 255 when reaching Router B. In the
GTSM statistics of Router B, the number of dropped packets increases accordingly.

----End

Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
interface GigabitEthernet1/0/0
ip address 10.1.1.1 255.255.255.0
#
bgp 10
router-id 1.1.1.9
peer 10.1.1.2 as-number 20
peer 10.1.1.2 valid-ttl-hops 1
#
ipv4-family unicast
undo synchronization
peer 10.1.1.2 enable
#
return

● Configuration file of Router B

#
sysname RouterB
#
interface GigabitEthernet1/0/0
ip address 10.1.1.2 255.255.255.0
#

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interface GigabitEthernet2/0/0
ip address 20.1.1.1 255.255.255.0
#
interface LoopBack0
ip address 2.2.2.9 255.255.255.255
#
bgp 20
router-id 2.2.2.9
peer 3.3.3.9 as-number 20
peer 3.3.3.9 valid-ttl-hops 1
peer 3.3.3.9 connect-interface LoopBack0
peer 4.4.4.9 as-number 20
peer 4.4.4.9 valid-ttl-hops 2
peer 4.4.4.9 connect-interface LoopBack0
peer 10.1.1.1 as-number 10
peer 10.1.1.1 valid-ttl-hops 1
#
ipv4-family unicast
undo synchronization
peer 3.3.3.9 enable
peer 3.3.3.9 next-hop-local
peer 4.4.4.9 enable
peer 4.4.4.9 next-hop-local
peer 10.1.1.1 enable
#
ospf 1
area 0.0.0.0
network 20.1.1.0 0.0.0.255
network 2.2.2.9 0.0.0.0
#
return
● Configuration file of Router C
#
sysname RouterC
#
interface GigabitEthernet1/0/0
ip address 20.1.1.2 255.255.255.0
#
interface GigabitEthernet2/0/0
ip address 20.1.2.1 255.255.255.0
#
interface LoopBack0
ip address 3.3.3.9 255.255.255.255
#
bgp 20
router-id 3.3.3.9
peer 2.2.2.9 as-number 20
peer 2.2.2.9 valid-ttl-hops 1
peer 2.2.2.9 connect-interface LoopBack0
peer 4.4.4.9 as-number 20
peer 4.4.4.9 valid-ttl-hops 1
peer 4.4.4.9 connect-interface LoopBack0
#
ipv4-family unicast
undo synchronization
peer 2.2.2.9 enable
peer 4.4.4.9 enable
#
ospf 1
area 0.0.0.0
network 20.1.2.0 0.0.0.255
network 20.1.1.0 0.0.0.255
network 3.3.3.9 0.0.0.0
#
return
● Configuration file of Router D
#
sysname RouterD

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#
interface GigabitEthernet1/0/0
ip address 20.1.2.2 255.255.255.0
#
interface LoopBack0
ip address 4.4.4.9 255.255.255.255
#
bgp 20
router-id 4.4.4.9
peer 2.2.2.9 as-number 20
peer 2.2.2.9 valid-ttl-hops 2
peer 2.2.2.9 connect-interface LoopBack0
peer 3.3.3.9 as-number 20
peer 3.3.3.9 valid-ttl-hops 1
peer 3.3.3.9 connect-interface LoopBack0
#
ipv4-family unicast
undo synchronization
peer 2.2.2.9 enable
peer 3.3.3.9 enable
#
ospf 1
area 0.0.0.0
network 20.1.2.0 0.0.0.255
network 4.4.4.9 0.0.0.0
#
return

9.20.15 Example for Configuring BFD for BGP4+

After BFD for BGP4+ is configured, BFD can fast detect the fault on the link
between BGP4+ peers and notify it to BGP4+ so that service traffic can be
transmitted through the backup link.

Networking Requirements
● As shown in Figure 9-40, Router A belongs to AS 100, Router B to AS 200,
and Router C to AS 200. Establish an EBGP connection between Router A and
Router B and that between Router A and Router C.
● Traffic is transmitted on the active link Router A → Router B. The link Router
A → Router C → Router B acts as the standby link.
● Use BFD to detect the BGP session between Router A and Router B. When the
link between Router A and Router B fails, BFD can rapidly detect the failure
and notify BGP of the failure. Traffic is transmitted on the standby link.

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Figure 9-40 Networking diagram of configuring BFD for BGP4+

GE3/0/0
2001:db8:7::1/64
GE2/0/0
2001:db8:8::2/64

GE1/0/0 EBGP GE1/0/0

AS 100 RouterB
2001:db8:8::1/64 2001:db8:9::1:1/64

RouterA IBGP
AS 200
GE2/0/0
2001:db8:10::1/64 EBGP GE1/0/0
2001:db8:9::1:2/64

GE2/0/0
2001:db8:10::2/64 RouterC

Configuration Roadmap
The configuration roadmap is as follows:
1. Configure the basic BGP4+ functions on each router.
2. Configure MED attributes to control the routing selection of the routers.
3. Enable the BFD on Router A and Router B.

Procedure
Step 1 Assign an IPv6 address to each interface.
The detailed configuration is not mentioned here.
Step 2 Configure the basic BGP4+ functions. Establish an EBGP connection between
Router A and Router B, that between Router A and Router C. Establish an IBGP
connection between Router B and Router C.
# Configure Router A.
[RouterA] bgp 100
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 2001:db8:8::2 as-number 200
[RouterA-bgp] peer 2001:db8:10::2 as-number 200
[RouterA-bgp] ipv6-family unicast
[RouterA-bgp-af-ipv6] peer 2001:db8:8::2 enable
[RouterA-bgp-af-ipv6] peer 2001:db8:10::2 enable
[RouterA-bgp-af-ipv6] quit
[RouterA-bgp] quit

# Configure Router B.
[RouterB] bgp 200
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 2001:db8:8::1 as-number 100
[RouterB-bgp] peer 2001:db8:9::1:2 as-number 200
[RouterB-bgp] ipv6-family unicast
[RouterB-bgp-af-ipv6] peer 2001:db8:8::1 enable

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[RouterB-bgp-af-ipv6] peer 2001:db8:9::1:2 enable

[RouterB-bgp-af-ipv6] network 2001:db8:7::1 64
[RouterB-bgp-af-ipv6] quit
[RouterB-bgp] quit

# Configure Router C.
[Routerc] bgp 200
[Routerc-bgp] router-id 3.3.3.3
[Routerc-bgp] peer 2001:db8:10::1 as-number 100
[Routerc-bgp] peer 2001:db8:9::1:1 as-number 200
[RouterC-bgp] ipv6-family unicast
[RouterC-bgp-af-ipv6] peer 2001:db8:10::1 enable
[RouterC-bgp-af-ipv6] peer 2001:db8:9::1:1 enable
[RouterC-bgp-af-ipv6] quit
[RouterC-bgp] quit

# Display the established BGP neighbors on Router A.

[RouterA] display bgp ipv6 peer

BGP local router ID : 1.1.1.1

Local AS number : 100
Total number of peers : 2 Peers in established state : 2

Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv

2001:db8:8::2 4 200 12 11 0 00:07:26 Established 0

2001:db8:10::2 4 200 12 12 0 00:07:21 Established 0

Step 3 Configure MED attributes.

Set the value of MED sent by Router B and Router C to Router A by using the
policy.
# Configure Router B.
[RouterB] route-policy 10 permit node 10
[RouterB-route-policy] apply cost 100
[RouterB-route-policy] quit
[RouterB] bgp 200
[RouterB-bgp] ipv6-family unicast
[RouterB-bgp-af-ipv6] peer 2001:db8:8::1 route-policy 10 export
[RouterB-bgp-af-ipv6] quit
[RouterB-bgp] quit

# Configure Router C.
[RouterC] route-policy 10 permit node 10
[RouterC-route-policy] apply cost 150
[RouterC-route-policy] quit
[RouterC] bgp 200
[RouterC-bgp] ipv6-family unicast
[RouterC-bgp-af-ipv6] peer 2001:db8:10::1 route-policy 10 export
[RouterC-bgp-af-ipv6] quit
[RouterC-bgp] quit

# Display all BGP routing information on Router A.

[RouterA] display bgp ipv6 routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 2

*> Network : 2001:db8:7:: PrefixLen : 64

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NextHop : 2001:db8:8::2 LocPrf :

MED : 100 PrefVal : 0
Label :
Path/Ogn : 200 i
*
NextHop : 2001:db8:10::2 LocPrf :
MED : 150 PrefVal : 0
Label :
Path/Ogn : 200 i

As shown in the BGP routing table, the next hop address of the route to
2001:db8:7::1/64 is 2001:db8:8::2 and traffic is transmitted on the active link
Router A → Router B.
Step 4 Configure the BFD detection function, the interval for sending the packets, the
interval for receiving the packets, and the local detection time multiple.
# Enable BFD on Router A, set the minimum interval for sending the packets and
the minimum interval for receiving the packets to 100 ms, and set the local
detection time multiple to 4.
[RouterA] bfd
[RouterA-bfd] quit
[RouterA] bgp 100
[RouterA-bgp] peer 2001:db8:8::2 bfd enable
[RouterA-bgp] peer 2001:db8:8::2 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4
[RouterA-bgp] quit

# Enable BFD on Router B, set the minimum interval for sending the packets and
the minimum interval for receiving the packets to 100 ms, and set the local
detection time multiple to 4.
[RouterB] bfd
[RouterB-bfd] quit
[RouterB] bgp 200
[RouterB-bgp] peer 2001:db8:8::1 bfd enable
[RouterB-bgp] peer 2001:db8:8::1 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4
[RouterB-bgp] quit

# Display all BFD sessions set up by BGP on Router A.

[RouterA] display bgp ipv6 bfd session all
Local_Address : 2001:db8:8::1
Peer_Address : 2001:db8:8::2
Tx-interval(ms): 100 Rx-interval(ms): 100
Multiplier :4 Interface : GigabitEthernet1/0/0
LD/RD : 8192/8192 Session-State : Up
Wtr-interval(m):0

Step 5 Verify the Configuration.

# Run the shutdown command on GE 2/0/0 of Router B to simulate the active
link failure.
[RouterB] interface gigabitethernet 2/0/0
[RouterB-Gigabitethernet2/0/0] shutdown

Step 6 # Display the routing table on Router A.

[RouterA] display bgp ipv6 routing-table

BGP Local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 1

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*> Network : 2001:db8:7:: PrefixLen : 64

NextHop : 2001:db8:10::2 LocPrf :
MED : 150 PrefVal : 0
Label :
Path/Ogn : 200 i

As shown in the BGP routing table, the standby link Router A → Router C →
Router B takes effect after the active link fails. The next hop address of the route
to 2001:db8:7::1/64 becomes 2001:db8:10::2.

----End

Configuration Files
● Configuration file of Router A
#
sysname RouterA
#
ipv6
#
bfd
#
interface GigabitEthernet1/0/0
undo shutdown
ipv6 enable
ipv6 address 2001:db8:8::1/64
#
interface GigabitEthernet2/0/0
undo shutdown
ipv6 enable
ipv6 address 2001:db8:10::1/64
#
interface NULL0
#
interface LoopBack0
ip address 1.1.1.1 255.255.255.255
#
bgp 100
router-id 1.1.1.1
peer 2001:db8:8::2 as-number 200
peer 2001:db8:8::2 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4
peer 2001:db8:8::2 bfd enable
peer 2001:db8:10::2 as-number 200
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
peer 2001:db8:8::2 enable
peer 2001:db8:10::2 enable
#
return

● Configuration file of Router B

#
sysname RouterB
#
sysname RouterB
#
ipv6
#
bfd
#
interface interface GigabitEthernet2/0/0
shutdown
ipv6 enable

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ipv6 address 2001:db8:8::2/64

#
interface GigabitEthernet1/0/0
undo shutdown
ipv6 enable
ipv6 address 2001:db8:9::1:1/64
#
interface GigabitEthernet3/0/0
undo shutdown
ipv6 enable
ipv6 address 2001:db8:7::1/64
#
interface NULL0
#
interface LoopBack0
ip address 2.2.2.2 255.255.255.255
#
bgp 200
router-id 2.2.2.2
peer 2001:db8:8::1 as-number 100
peer 2001:db8:8::1 bfd min-tx-interval 100 min-rx-interval 100 detect-multiplier 4
peer 2001:db8:8::1 bfd enable
peer 2001:db8:9::1:2 as-number 200
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
network 2001:db8:7:: 64
peer 2001:db8:8::1 enable
peer 2001:db8:8::1 route-policy 10 export
peer 2001:db8:9::1:2 enable
#
route-policy 10 permit node 10
apply cost 100
#
return
● Configuration file of Router C
#
sysname RouterC
#
ipv6
#
interface interface GigabitEthernet1/0/0
undo shutdown
ipv6 enable
ipv6 address 2001:db8:9::1:2/64
#
interface interface GigabitEthernet2/0/0
undo shutdown
ipv6 enable
ipv6 address 2001:db8:10::2/64
#
interface LoopBack0
ip address 3.3.3.3 255.255.255.255
#
bgp 200
router-id 3.3.3.3
peer 2001:db8:9::1:1 as-number 200
peer 2001:db8:10::1 as-number 100
#
ipv4-family unicast
undo synchronization
#
ipv6-family unicast
undo synchronization
peer 2001:db8:9::1:1 enable
peer 2001:db8:10::1 enable

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peer 2001:db8:10::1 route-policy 10 export

#
route-policy 10 permit node 10
apply cost 150
#
return

9.21 FAQ About BGP

9.21.1 Why Are Loopback Addresses Used to Establish BGP

Peer Relationships?
Loopback interfaces are logical interfaces. Compared with physical interfaces,
loopback interfaces are not affected by links and can reduce the Border Gateway
Protocol (BGP) flapping.

9.21.2 Why Is the BGP Connection Not Interrupted

Immediately After the Interfaces Connecting Two Peers Are
Shut Down?
When External Border Gateway Protocol (EBGP) peers are directly connected and
the ebgp-interface-sensitive command is run in the Border Gateway Protocol
(BGP) view, the BGP peer relationship is interrupted immediately after the
interfaces connecting the two peers are shut down. By default, the ebgp-
interface-sensitive command is run in the BGP view. In other cases, the BGP peer
relationship is not interrupted until the Hold timer times out.

9.21.3 Why Are All the Next Hop Addresses in the BGP
Routing Table Displayed as 0.0.0.0 After BGP Imports Routes
from Other Protocols?
Only routes that exist in the Border Gateway Protocol (BGP) routing table can be
imported by the BGP. When importing such routes, BGP does not add new routes,
but increases the reference count based on the routing table.

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