Basic Router Configuration

This section includes information about some basic router configuration, and contains the following sections:
• Default Configuration, on page 1
• Configuring Global Parameters, on page 3
• Configuring Gigabit Ethernet Interfaces, on page 3
• Configuring a Loopback Interface, on page 4
• Hardware Limitations for MAC Filters, on page 6
• Configuring Module Interfaces, on page 8
• Enabling Cisco Discovery Protocol, on page 8
• Configuring Command-Line Access, on page 8
• Configuring Static Routes, on page 10
• Configuring Dynamic Routes, on page 12

Default Configuration
When you boot up the router, the router looks for a default file name-the PID of the router. For example, the
Cisco 4000 Series Integrated Services Routers look for a file named isr 4451.cfg. The Cisco 4000 Series ISR
looks for this file before finding the standard files-router-confg or the ciscortr.cfg.
The Cisco 4000 ISR looks for the isr4451.cfg file in the bootflash. If the file is not found in the bootflash, the
router then looks for the standard files-router-confg and ciscortr.cfg. If none of the files are found, the router
then checks for any inserted USB that may have stored these files in the same particular order.

Note If there is a configuration file with the PID as its name in an inserted USB, but one of the standard files are
in bootflash, the system finds the standard file for use.

Use the show running-config command to view the initial configuration, as shown in the following example:
Router# show running-config
Building configuration...
Current configuration : 977 bytes
!
version 15.3
service timestamps debug datetime msec
service timestamps log datetime msec
no platform punt-keepalive disable-kernel-core
!

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1
 Basic Router Configuration
Default Configuration

hostname Router
!
boot-start-marker
boot-end-marker
!
!
vrf definition Mgmt-intf
!
address-family ipv4
exit-address-family
!
address-family ipv6
exit-address-family
!
!
no aaa new-model
!
ipv6 multicast rpf use-bgp
!
!
multilink bundle-name authenticated
!
!
redundancy
mode none
!

interface GigabitEthernet0/0/0
no ip address
negotiation auto
!
interface GigabitEthernet0/0/1
no ip address
negotiation auto
!
interface GigabitEthernet0/0/2
no ip address
negotiation auto
!
interface GigabitEthernet0/0/3
no ip address
negotiation auto
!
interface GigabitEthernet0
vrf forwarding Mgmt-intf
no ip address
negotiation auto
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!

!
control-plane
!
!
line con 0
stopbits 1
line vty 0 4
login
!
!

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 Basic Router Configuration
Configuring Global Parameters

end

Configuring Global Parameters

To configure the global parameters for your router, follow these steps.

SUMMARY STEPS
1. configure terminal
2. hostname name
3. enable secret password
4. no ip domain-lookup

DETAILED STEPS

Command or Action Purpose

Step 1 configure terminal Enters global configuration mode when using the console
port.
Example:
Use the following to connect to the router with a remote
Router> enable terminal:
Router# configure terminal
Router(config)# telnet router-name or address
Login: login-id
Password: *********
Router> enable

Step 2 hostname name Specifies the name for the router.

Example:

Router(config)# hostname Router

Step 3 enable secret password Specifies an encrypted password to prevent unauthorized

access to the router.
Example:

Router(config)# enable secret cr1ny5ho

Step 4 no ip domain-lookup Disables the router from translating unfamiliar words (typos)
into IP addresses.
Example:
For complete information on global parameter commands,
Router(config)# no ip domain-lookup see the Cisco IOS Release Configuration Guide
documentation set.

Configuring Gigabit Ethernet Interfaces

To manually define onboard Gigabit Ethernet interfaces, follow these steps, beginning from global configuration
mode.

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 Basic Router Configuration
Configuring a Loopback Interface

SUMMARY STEPS
1. interface gigabitethernet slot/bay/port
2. ip address ip-address mask
3. ipv6 address ipv6-address/prefix
4. no shutdown
5. exit

DETAILED STEPS

Command or Action Purpose

Step 1 interface gigabitethernet slot/bay/port Enters the configuration mode for a Gigabit Ethernet
interface on the router.
Example:

Router(config)# interface gigabitethernet 0/0/1

Step 2 ip address ip-address mask Sets the IP address and subnet mask for the specified
Gigabit Ethernet interface. Use this Step if you are
Example:
configuring an IPv4 address.
Router(config-if)# ip address 192.168.12.2
255.255.255.0

Step 3 ipv6 address ipv6-address/prefix Sets the IPv6 address and prefix for the specified Gigabit
Ethernet interface. Use this step instead of Step 2, if you
Example:
are configuring an IPv6 address.
Router(config-if)# ipv6 address
2001.db8::ffff:1/128

Step 4 no shutdown Enables the Gigabit Ethernet interface and changes its state
from administratively down to administratively up.
Example:

Router(config-if)# no shutdown

Step 5 exit Exits configuration mode for the Gigabit Ethernet interface
and returns to privileged EXEC mode.
Example:

Router(config-if)# exit

Configuring a Loopback Interface

Before you begin
The loopback interface acts as a placeholder for the static IP address and provides default routing information.
To configure a loopback interface, follow these steps.

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 Basic Router Configuration
Configuring a Loopback Interface

SUMMARY STEPS
1. interface type number
2. (Option 1) ip address ip-address mask
3. (Option 2) ipv6 address ipv6-address/prefix
4. exit

DETAILED STEPS

Command or Action Purpose

Step 1 interface type number Enters configuration mode on the loopback interface.
Example:

Router(config)# interface Loopback 0

Step 2 (Option 1) ip address ip-address mask Sets the IP address and subnet mask on the loopback
interface. (If you are configuring an IPv6 address, use the
Example:
ipv6 address ipv6-address/prefix command described
below.
Router(config-if)# ip address 10.108.1.1
255.255.255.0

Step 3 (Option 2) ipv6 address ipv6-address/prefix Sets the IPv6 address and prefix on the loopback interface.
Example:

Router(config-if)# 2001:db8::ffff:1/128

Step 4 exit Exits configuration mode for the loopback interface and
returns to global configuration mode.
Example:

Router(config-if)# exit

Example

Verifying Loopback Interface Configuration

The loopback interface in this sample configuration is used to support Network Address Translation
(NAT) on the virtual-template interface. This configuration example shows the loopback interface
configured on the Gigabit Ethernet interface with an IP address of 192.0.2.0/24, which acts as a static
IP address. The loopback interface points back to virtual-template1, which has a negotiated IP address.
!
interface loopback 0
ip address 192.0.2.0 255.255.255.0 (static IP address)
ip nat outside
!
interface Virtual-Template1
ip unnumbered loopback0
no ip directed-broadcast
ip nat outside

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 Basic Router Configuration
Hardware Limitations for MAC Filters

Enter the show interface loopback command. You should see an output similar to the following
example:

Router# show interface loopback 0

Loopback0 is up, line protocol is up
Hardware is Loopback
Internet address is 203.0.113.1/24
MTU 1514 bytes, BW 8000000 Kbit, DLY 5000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation LOOPBACK, loopback not set
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/0, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out

Alternatively, use the ping command to verify the loopback interface, as shown in the following
example:

Router# ping 192.0.2.0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.0, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

Hardware Limitations for MAC Filters

This section provides the number and distribution of supported virtual MAC addresses on the Cisco 4000
Series ISRs. The virtual MAC address filters are supported on the following interfaces:
• GigabitEthernet Interface MAC Filters
• TenGigabitEthernet Interface MAC Filters

GigabitEthernet Interface MAC Address Filters

The device supports a set of 32 MAC address filters. You can be use these filters across the four GE ports.
Each 4 GEport reserves one entry for the primary MAC address (BIA). You can use the remaining 28 MAC
filters for features such as Hot Standby Router Protocol (HSRP).

Note Each port can use any number of the available feature filters. A single port can use a maximum of 28 feature
filters. If all the 4 GE ports uses the filters equally, then each port can have a maximum of seven filters.

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 Basic Router Configuration
MAC Filter Distribution

TenGigabitEthernet Interface MAC Address Filters

The device supports a set of 32 MAC address filters. You can be use these filters across the two 10GE ports.
Each 10GE port reserves one entry for the primary MAC address (BIA). You can use the remaining 30 MAC
filters for features such as HSRP.

Note Each port can use any number of the available feature filters. A single port can use a maximum of 30 feature
filters. If both the ports uses the filters equally, then each port can have a maximum of 15 filters.

MAC Filter Distribution

The following tables provide the MAC filter distribution for the Cisco 4000 Series ISRs:

Table 1: Cisco 4461 ISR MAC Filter Distribution

Interface Total Filters Primary MAC Feature Filters

Address (BIA)

Gigabit0/0/0 32 = 1 + 28

Gigabit0/0/1 1

Gigabit0/0/2 1

Gigabit0/0/3 1

TenGigabit0/0/0 32 = 1 + 30

TenGigabit0/0/1 1

Table 2: Cisco 4451 and 4431 ISRs GigabitEthernet Interface MAC Filters Distribution

Interface Total Filters Primary MAC Feature Filters

Address (BIA)

Gigabit0/0/0 32 = 1 + 28

Gigabit0/0/1 1

Gigabit0/0/2 1

Gigabit0/0/3 1

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 Basic Router Configuration
Configuring Module Interfaces

Table 3: Cisco ISR4351 and 4331 ISR MAC Filter Distribution

Interface Total Filters Primary MAC Feature Filters

Address (BIA)

Gigabit0/0/0 16 = 1 + 15

Gigabit0/0/1 16 1 15

Gigabit0/0/2 16 1 15

Table 4: Cisco 4321 and 4221 ISRs MAC Filter Distribution

Interface Total Filters Primary MAC Feature Filters

Address (BIA)

Gigabit0/0/0 16 = 1 + 15

Gigabit0/0/1 16 = 1 + 15

Configuring Module Interfaces

For detailed information about configuring service modules, see "Service Modules" in the "Service Module
Management" section of the Cisco SM-1T3/E3 Service Module Configuration Guide.

Enabling Cisco Discovery Protocol

Cisco Discovery Protocol (CDP) is enabled by default on the router.

Note CDP is not enabled by default on Cisco Aggregation Services Routers or on the Cisco CSR 1000v.

For more information on using CDP, see Cisco Discovery Protocol Configuration Guide, Cisco IOS XE
Release 3S.

Configuring Command-Line Access

To configure parameters to control access to the router, follow these steps.

SUMMARY STEPS
1. line [aux | console | tty | vty] line-number
2. password password
3. login
4. exec-timeout minutes [seconds]
5. exit

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 Basic Router Configuration
Configuring Command-Line Access

6. line [aux | console | tty | vty] line-number

7. password password
8. login
9. end

DETAILED STEPS

Command or Action Purpose

Step 1 line [aux | console | tty | vty] line-number Enters line configuration mode, and specifies the type of
line.
Example:
The example provided here specifies a console terminal for
Router(config)# line console 0 access.

Step 2 password password Specifies a unique password for the console terminal line.
Example:

Router(config-line)# password 5dr4Hepw3

Step 3 login Enables password checking at terminal session login.

Example:

Router(config-line)# login

Step 4 exec-timeout minutes [seconds] Sets the interval during which the EXEC command
interpreter waits until user input is detected. The default is
Example:
10 minutes. Optionally, adds seconds to the interval value.
Router(config-line)# exec-timeout 5 30 The example provided here shows a timeout of 5 minutes
Router(config-line)# and 30 seconds. Entering a timeout of 0 0 specifies never
to time out.

Step 5 exit Exits line configuration mode to re-enter global

configuration mode.
Example:

Router(config-line)# exit

Step 6 line [aux | console | tty | vty] line-number Specifies a virtual terminal for remote console access.
Example:

Router(config)# line vty 0 4

Router(config-line)#

Step 7 password password Specifies a unique password for the virtual terminal line.
Example:

Router(config-line)# password aldf2ad1

Step 8 login Enables password checking at the virtual terminal session

login.
Example:

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 Basic Router Configuration
Configuring Static Routes

Command or Action Purpose

Router(config-line)# login

Step 9 end Exits line configuration mode, and returns to privileged

EXEC mode.
Example:

Router(config-line)# end

Example
The following configuration shows the command-line access commands.
You do not have to input the commands marked default. These commands appear automatically in
the configuration file that is generated when you use the show running-config command.
!
line console 0
exec-timeout 10 0
password 4youreyesonly
login
transport input none (default)
stopbits 1 (default)
line vty 0 4
password secret
login
!

Configuring Static Routes

Static routes provide fixed routing paths through the network. They are manually configured on the router. If
the network topology changes, the static route must be updated with a new route. Static routes are private
routes unless they are redistributed by a routing protocol.
To configure static routes, follow these steps.

SUMMARY STEPS
1. (Option 1) ip route prefix mask {ip-address | interface-type interface-number [ip-address]}
2. (Option 2) ipv6 route prefix/mask {ipv6-address | interface-type interface-number [ipv6-address]}
3. end

DETAILED STEPS

Command or Action Purpose

Step 1 (Option 1) ip route prefix mask {ip-address | Specifies a static route for the IP packets. (If you are
interface-type interface-number [ip-address]} configuring an IPv6 address, use the ipv6 route command
described below.)
Example:

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 Basic Router Configuration
Configuring Static Routes

Command or Action Purpose

Router(config)# ip route 192.168.1.0 255.255.0.0

10.10.10.2

Step 2 (Option 2) ipv6 route prefix/mask {ipv6-address | Specifies a static route for the IP packets.
interface-type interface-number [ipv6-address]}
Example:

Router(config)# ipv6 route 2001:db8:2::/64

Step 3 end Exits global configuration mode and enters privileged EXEC
mode.
Example:

Router(config)# end

Example

Verifying Configuration
In the following configuration example, the static route sends out all IP packets with a destination
IP address of 192.168.1.0 and a subnet mask of 255.255.255.0 on the Gigabit Ethernet interface to
another device with an IP address of 10.10.10.2. Specifically, the packets are sent to the configured
PVC.
You do not have to enter the command marked default. This command appears automatically in the
configuration file generated when you use the running-config command.
!
ip classless (default)
ip route 192.168.1.0 255.255.255.0

To verify that you have configured static routing correctly, enter the show ip route command (or
show ipv6 route command) and look for static routes marked with the letter S.
When you use an IPv4 address, you should see verification output similar to the following:

Router# show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

10.10.10.2/24 is subnetted, 1 subnets

C 10.10.10.2 is directly connected, Loopback0
S* 0.0.0.0/0 is directly connected, FastEthernet0

When you use an IPv6 address, you should see verification output similar to the following:

Router# show ipv6 route

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 Basic Router Configuration
Configuring Dynamic Routes

IPv6 Routing Table - default - 5 entries

Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, R - RIP, H - NHRP, I1 - ISIS L1
I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary, D - EIGRP
EX - EIGRP external, ND - ND Default, NDp - ND Prefix, DCE -
Destination
NDr - Redirect, O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1
OE2 - OSPF ext 2, ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
ls - LISP site, ld - LISP dyn-EID, a - Application

C 2001:DB8:3::/64 [0/0]
via GigabitEthernet0/0/2, directly connected
S 2001:DB8:2::/64 [1/0]
via 2001:DB8:3::1

Configuring Dynamic Routes

In dynamic routing, the network protocol adjusts the path automatically, based on network traffic or topology.
Changes in dynamic routes are shared with other routers in the network.
A router can use IP routing protocols, such as Routing Information Protocol (RIP) or Enhanced Interior
Gateway Routing Protocol (EIGRP), to learn about routes dynamically.
• Configuring Routing Information Protocol, on page 12
• Configuring Enhanced Interior Gateway Routing Protocol, on page 15

Configuring Routing Information Protocol

To configure the RIP on a router, follow these steps.

SUMMARY STEPS
1. router rip
2. version {1 | 2}
3. network ip-address
4. no auto-summary
5. end

DETAILED STEPS

Command or Action Purpose

Step 1 router rip Enters router configuration mode, and enables RIP on the
router.
Example:

Router(config)# router rip

Step 2 version {1 | 2} Specifies use of RIP version 1 or 2.

Example:

Router(config-router)# version 2

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 Basic Router Configuration
Configuring Routing Information Protocol

Command or Action Purpose

Step 3 network ip-address Specifies a list of networks on which RIP is to be applied,

using the address of the network of each directly connected
Example:
network.
Router(config-router)# network 192.168.1.1
Router(config-router)# network 10.10.7.1

Step 4 no auto-summary Disables automatic summarization of subnet routes into

network-level routes. This allows subprefix routing
Example:
information to pass across classful network boundaries.
Router(config-router)# no auto-summary

Step 5 end Exits router configuration mode, and enters privileged

EXEC mode.
Example:

Router(config-router)# end

Example

Verifying Configuration
The following configuration example shows RIP Version 2 enabled in IP networks 10.0.0.0 and
192.168.1.0. To see this configuration, use the show running-config command from privileged
EXEC mode.
!
Router# show running-config
Building configuration...

Current configuration : 1616 bytes

!
! Last configuration change at 03:17:14 EST Thu Sep 6 2012
!
version 15.3
service timestamps debug datetime msec
service timestamps log datetime msec
no platform punt-keepalive disable-kernel-core
!
hostname Router
!
boot-start-marker
boot-end-marker
!
!
vrf definition Mgmt-intf
!
address-family ipv4
exit-address-family
!
address-family ipv6
exit-address-family
!
enable password cisco
!

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 Basic Router Configuration
Configuring Routing Information Protocol

no aaa new-model
!
transport-map type console consolehandler
banner wait ^C
Waiting for IOS vty line
^C
banner diagnostic ^C
Welcome to diag mode
^C
!
clock timezone EST -4 0
!
!

ip domain name cisco.com

ip name-server vrf Mgmt-intf 203.0.113.1
ip name-server vrf Mgmt-intf 203.0.113.129

!
ipv6 multicast rpf use-bgp
!
!
multilink bundle-name authenticated
!
redundancy
mode none
!
ip ftp source-interface GigabitEthernet0
ip tftp source-interface GigabitEthernet0
!
!
interface GigabitEthernet0/0/0
no ip address
negotiation auto
!
interface GigabitEthernet0/0/1
no ip address
negotiation auto
!
interface GigabitEthernet0/0/2
no ip address
negotiation auto
!
interface GigabitEthernet0/0/3
no ip address
negotiation auto
!
interface GigabitEthernet0
vrf forwarding Mgmt-intf
ip address 172.18.77.212 255.255.255.240
negotiation auto
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
ip route vrf Mgmt-intf 0.0.0.0 0.0.0.0 172.18.77.209
!
control-plane
!
!
line con 0
stopbits 1

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 Basic Router Configuration
Configuring Enhanced Interior Gateway Routing Protocol

line aux 0
stopbits 1
line vty 0 4
password cisco
login
!
transport type console 0 input consolehandler
!
ntp server vrf Mgmt-intf 10.81.254.131
!
end

To verify that you have configured RIP correctly, enter the show ip route command and look for
RIP routes marked with the letter R. You should see an output similar to the one shown in the
following example:
Router# show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

10.0.0.0/24 is subnetted, 1 subnets

C 10.108.1.0 is directly connected, Loopback0
R 10.0.0.0/8 [120/1] via 10.2.2.1, 00:00:02, Ethernet0/0/0

Configuring Enhanced Interior Gateway Routing Protocol

To configure Enhanced Interior Gateway Routing Protocol (EIGRP), follow these steps.

SUMMARY STEPS
1. router eigrp as-number
2. network ip-address
3. end

DETAILED STEPS

Command or Action Purpose

Step 1 router eigrp as-number Enters router configuration mode, and enables EIGRP on
the router. The autonomous-system number identifies the
Example:
route to other EIGRP routers and is used to tag the EIGRP
information.
Router(config)# router eigrp 109

Step 2 network ip-address Specifies a list of networks on which EIGRP is to be

applied, using the IP address of the network of directly
Example:
connected networks.
Router(config)# network 192.168.1.0
Router(config)# network 10.10.12.115

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 Basic Router Configuration
Configuring Enhanced Interior Gateway Routing Protocol

Command or Action Purpose

Step 3 end Exits router configuration mode, and enters privileged
EXEC mode.
Example:

Router(config-router)# end

Example

Verifying the Configuration

The following configuration example shows the EIGRP routing protocol enabled in IP networks
192.168.1.0 and 10.10.12.115. The EIGRP autonomous system number is 109. To see this
configuration, use the show running-config command.
Router# show running-config
.
.
.
!
router eigrp 109
network 192.168.1.0
network 10.10.12.115
!
.
.
.

To verify that you have configured IP EIGRP correctly, enter the show ip route command, and look
for EIGRP routes marked by the letter D. You should see verification output similar to the following:
Router# show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

10.0.0.0/24 is subnetted, 1 subnets

C 10.108.1.0 is directly connected, Loopback0
D 10.0.0.0/8 [90/409600] via 10.2.2.1, 00:00:02, Ethernet0/0

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