IPv6 Address

Representation

1
IPv6 Address Notation: Example

128.91.45.157.220.40.0.0.0.0.252.87.212.200.31.255

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Rule 1- IPv6 Zero Suppression
 Some types of addresses contain long sequences of zeros.
 To further simplify the representation of IPv6 addresses, a
contiguous sequence of 16-bit blocks set to 0 in the colon
hexadecimal format can be compressed to “::”, known as
double-colon.

 For example:
 link-local address
 FE80:0:0:0:2AA:FF:FE9A:4CA2  FE80::2AA:FF:FE9A:4CA2.
 multicast address
 FF02:0:0:0:0:0:0:2  FF02::2
 loopback address
 0:0:0:0:0:0:0:1  ::1

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Rule 1- IPv6 Zero Suppression
 Zero compression can only be used to compress a single
contiguous series of 16-bit blocks expressed in colon
hexadecimal notation.
 You cannot use zero compression to include part of a 16-bit
block.

 For example,
 cannot express FF02:30:0:0:0:0:0:5 as FF02:3::5
 correct representation = FF02:30::5
 Leading zeroes in every group can be omitted.
2001:718:1c01:16:20d:56ff:fe77:52a3

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Rule 1- IPv6 Zero Suppression
 To determine the number of 0 bits represented by the “::”
1. count the number of blocks in the compressed address
2. (-) subtract this number from 8
3. (*) multiply the result by 16.

 For example
1. FF02::2
2. two blocks - “FF02” block and “2” block.
3. The number of bits expressed by the “::” is 96 (96 = (8 – 2)16).

 Zero compression can only be used once in a given

address.
 Otherwise, you could not determine the number of 0 bits
represented by each instance of “::”.

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IPv6 Address Types

6
IPv6 Addresses: Types and
Scopes

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IPv6 Address Categories

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IPv6 Address Types

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Unicast IPv6 Addresses
 The following types of addresses are unicast
IPv6 addresses:
 Global unicast addresses
 Link-local addresses
 Site-local addresses
 Special addresses

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Global Unicast Addresses
 Equivalent to public IPv4 addresses.
 Globally routable and reachable on the IPv6 portion of the Internet.
 Unlike the current IPv4-based Internet, which is a mixture of both flat and
hierarchical routing, the IPv6-based Internet has been designed from its
foundation to support efficient, hierarchical addressing and routing.
 The scope, the portion of the IPv6 internetwork over which the address is
unique, of a global unicast address is the entire IPv6 Internet.
 Global scoped communication are identified by high-level 3 bits set to 001 (2000::/3)

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Global Unicast Address
 Each aggregatable global unicast IPv6 address has three parts:
 Fixed portion set to 001 – The three high-order bits are set to 001. The
address prefix for currently assigned global addresses is 2000::/3.
 Global Routing Prefix – Site Prefix
 Site prefix assigned to an organization (leaf site) by a provider should be at
least a /48 prefix = 45 + high-order bits (001).
 /48 prefix represents the high-order 48-bit of the network prefix.
 prefix assigned to the organization is part of the provider’s prefix.
 Subnet-id - Site
 With one /48 prefix allocated to an organization by a provider, it is possible
for that organization to enable up to 65,535 subnets (assignment of 64-bit’s
prefix to subnets).
 The organization can use bits 49 to 64 (16-bit) of the prefix received for
subnetting.
 Interface-id – Host
 The host part uses each node’s interface identifier.
 This part of the IPv6 address, which represents the address’s low-order 64-
bit, is called the interface ID.

IPv6 Addressing 12
Global Unicast Address: Example

2001:0410:0110::/48 is assigned by a provider

2001:0410:0110:0002::/64 network subnet within the
organization
2001:0410:0110:0002:0200:CBCF:1234:4402 – node address
within the subnet

IPv6 Addressing 13
IPv6 Unicast Address Scopes
 Three types of scopes:
1. Link-local scope
 Identifies all hosts within a single layer 2 domain.

 Called as link-local addresses

2. Unique-local scope
 Identifies all devices reachable within an administrative

site or domain typically contains multiple distinct links.

 Called as unique-local addresses (ULAs)

3. Global scope
 Identifies all devices reachable across the Internet.

 Called as global unicast addresses (GUAs)

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Local-Use Unicast Addresses
 There are two types of local-use unicast
addresses:
1. Link-local addresses
 used between on-link neighbors and for Neighbor
Discovery Processes.
2. Site-local addresses
 used between nodes communicating with other
nodes in the same site.

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Link-local Unicast Address
 Used only between nodes connected on the same local link.
 When an IPv6 stack is enabled on a node, one link-local address is
automatically assigned to each interface of the node at boot time.
 IPv6 link-local prefix FE80::/10 is used and the interface identifier in
Extended Unique Identifier 64 (EUI-64) format is appended as the
address’s low-order 64-bit.
 Bits 11 through 64 are set to 0 (54-bit).
 Link-local addresses are only for local-link scope and must never be
routed between subnets within a site.

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Site-Local Address
 Site-local addresses are equivalent to the IPv4 private address
space (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16).
 Private intranets that do not have a direct, routed connection to
the IPv6 Internet can use site-local addresses without conflicting
with global unicast addresses.
 Site-local addresses are not reachable from other sites, and
routers must not forward site-local traffic outside the site.
 Site-local addresses can be used in addition to global unicast
addresses.
 The scope of a site-local address is the site.
 A site is an organization network or portion of an organization's
network that has a defined geographical location (such as an
office, an office complex, or a campus).

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Site-Local Address
 Unlike link-local addresses, site-local addresses are not
automatically configured and must be assigned either through
stateless or stateful address configuration processes.
 May be assigned to any nodes and routers within a site.

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Special IPv6 Addresses
 The following are special IPv6 addresses:
 Unspecified address
 unspecified address (0:0:0:0:0:0:0:0 or ::) is only used to indicate
the absence of an address.
 equivalent to the IPv4 unspecified address of 0.0.0.0.
 used as a source address for packets attempting to verify the
uniqueness of a tentative address.
 never assigned to an interface or used as a destination address.
 Loopback address
 The loopback address (0:0:0:0:0:0:0:1 or ::1) is used to identify a
loopback interface, enabling a node to send packets to itself.
 It is equivalent to the IPv4 loopback address of 127.0.0.1.
 Packets addressed to the loopback address must never be sent
on a link or forwarded by an IPv6 router.

IPv6 Addressing 19
 Multicast
Addresses

20
Multicast Address: Overview
 In IPv6, multicast traffic operates in the same way that it does in
IPv4.
 Arbitrarily located IPv6 nodes can listen for multicast traffic on an
arbitrary IPv6 multicast address.
 IPv6 nodes can listen to multiple multicast addresses at the
same time.
 Nodes can join or leave a multicast group at any time.
 IPv6 multicast addresses have the first eight bits set to 1111
1111.
 An IPv6 address is easy to classify as multicast because it
always begins with “FF”.
 Multicast addresses cannot be used as source addresses or as
intermediate destinations in a Routing extension header.
 Beyond the first eight bits, multicast addresses include additional
structure to identify their flags, scope, and multicast group.
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Multicast Address
 Main goal of multicasting is having an efficient network to save
bandwidth on links by optimizing the number of packets
exchanged between nodes
 In IPv4:
 224.0.0.0/3, where the high-order 3-bit of the IPv4 address is set to 111
 In IPv6:

IPv6 Addressing 22
Multicast Address
 IPv6 makes heavy use of multicast addresses in the
mechanisms of the protocol such as
 The replacement of Address Resolution Protocol (ARP) in
IPv4
 Prefix advertisement
 Duplicate Address Detection (DAD)
 Prefix renumbering.
 Format of the multicast address defines several
scopes and types of addresses using the 4-bit fields
Flag and Scope.
 These fields are located after the FF::/8 prefix.
 The low-order 112-bit of the multicast address is the
multicast group ID.
IPv6 Addressing 23
Format of the Multicast Address
fields

High-order 3-bit of the Flag ield is reserved and must be initialized

using 0 values.
Remaining bit indicates the type of multicast address.

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Format of the Multicast Address:
Flags field
 Indicates flags set on the multicast address.
 The size = 4 bits.
 The first low-order bit = Transient (T) flag.
 T = 0  T flag indicates that the multicast address is a permanently assigned
(well-known) multicast address allocated by IANA.
 T = 1  T flag indicates that the multicast address is a transient (non-
permanently-assigned) multicast address.
 The second low-order bit = Prefix (P) flag
 indicates whether the multicast address is based on a unicast
address prefix.
 The third low-order bit = Rendezvous Point Address (R) flag
 indicates whether the multicast address contains an embedded rendezvous
point address.

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Format of the Multicast Address:
Scope Field
 Indicates the scope of the IPv6 internetwork for which the
multicast traffic is intended.
 The size = 4 bits.
 In addition to information provided by multicast routing protocols,
routers use the multicast scope to determine whether multicast
traffic can be forwarded.
 The most prevalent values for the Scope field are:
1. 1 (interface-local scope)
2. 2 (link-local scope)
3. 5 (site-local scope)
 For example:
 Traffic with the multicast address of FF02::2 has a link-local
scope.
 An IPv6 router never forwards this traffic beyond the local link.

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Format of the Multicast Address:
Scope Field

Example of Multicast Addresses with Different Scopes

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Format of the Multicast Address:
Group ID Field
 Identifies the multicast group and is unique within
the scope.
 The size = 112 bits.
 Permanently assigned group IDs are independent of
the scope.
 Transient group IDs are only relevant to a specific
scope.
 Multicast addresses from FF01:: through FF0F:: are
reserved, well-known addresses.

IPv6 Addressing 28
Multicast Assigned Address

 RFC 2373 defines and reserves several IPv6

addresses within the multicast scope for the
operation of the IPv6 protocol.
 These reserved addresses are called multicast
assigned addresses.
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Solicited-Node Multicast Address
 For each unicast and anycast address configured on an interface of a
node or router, a corresponding solicited-node multicast address is
automatically enabled.
 The solicited-node multicast address is scoped to the local link.
 Replacement of ARP in IPv4
 ARP is not used in IPv6, the solicited-node multicast address is used by
nodes and routers to learn the link-layer addresses of neighbor nodes and
routers on the same local link.
 As with ARP in IPv4, knowledge of link-layer addresses of neighbor nodes is
mandatory to make link-layer frames to deliver IPv6 packets.
 Duplicate Address Detection (DAD)
 DAD is part of NDP.
 It allows a node to verify whether an IPv6 address is already in use on its
local link before using that address to configure its own IPv6 address with
stateless autoconfiguration.
 The solicited-node multicast address is used to probe the local link in search
of a specific unicast or anycast address already configured on another node.

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Solicited-Node Multicast Address
Representations
Consists of the prefix FF02::1:FF00:0000/104 + low-order 24-
bit of the unicast or anycast address.

Low-order 24-bit of the unicast or anycast address is appended

to the prefix FF02::1:FF.

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Solicited-Node Multicast Address
Representations

Examples of Solicited-Node Multicast Addresses Made from Unicast

Addresses

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Anycast Address

33
Anycast Address
 Anycast addresses can be considered a conceptual cross
between unicast and multicast addressing.
 Unicast  send to this one address
 Multicast  send to every member of this group
 Anycast  send to any one member of this group
 In choosing which member to send to, for efficiency reasons
normally send to the closest one - closest in routing terms.
 So, anycast mean “send to the closest member of this group”.
 The network itself plays the key role in anycast by routing the
packet to the nearest destination by measuring network distance.
 Anycast addresses use aggregatable global unicast addresses.
 They can also use site-local or link-local addresses.
 Note that it is impossible to distinguish an anycast address from
a unicast address.
IPv6 Addressing 34
 So, How many IPv6
addresses can a host
have?

35
IPv6 Addresses for a Host
 An IPv4 host with a single network adapter typically
has a single IPv4 address assigned to that adapter.
 An IPv6 host, however, usually has multiple IPv6
addresses - even with a single interface.
 An IPv6 host is assigned the following unicast
addresses:
1. A link-local address for each interface
2. Unicast addresses for each interface (which could be a
site-local address and one or multiple global unicast
addresses)
3. The loopback address (::1) for the loopback interface

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IPv6 Addresses for a Host
 Typical IPv6 hosts are logically multihomed because they
have at least two addresses with which they can receive packets
1. a link-local address for local link traffic
2. a routable site-local or global address.
 Additionally, each host is listening for traffic on the following
multicast addresses:
1. The interface-local scope all-nodes multicast address (FF01::1)
2. The link-local scope all-nodes multicast address (FF02::1)
3. The solicited-node address for each unicast address on each
interface
4. The multicast addresses of joined groups on each interface

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 And, How many IPv6
addresses can a router
have?

38
IPv6 Addresses for a Router
 An IPv6 router is assigned the following
unicast addresses:
 A link-local address for each interface
 Unicast addresses for each interface (which could
be a site-local address and one or multiple global
unicast addresses)
 A Subnet-Router anycast address
 Additional anycast addresses (optional)
 The loopback address (::1) for the loopback
interface

IPv6 Addressing 39
IPv6 Addresses for a Router
 Additionally, each router is listening for traffic on the
following multicast addresses:
 The interface-local scope all-nodes multicast address
(FF01::1)
 The interface-local scope all-routers multicast address
(FF01::2)
 The link-local scope all-nodes multicast address (FF02::1)
 The link-local scope all-routers multicast address (FF02::2)
 The site-local scope all-routers multicast address (FF05::2)
 The solicited-node address for each unicast address on
each interface
 The multicast addresses of joined groups on each interface
IPv6 Addressing 40
IPv6 Interface Identifiers
 The last 64 bits of an IPv6 address are the interface identifier
that is unique to the 64-bit prefix of the IPv6 address.
 The following are the ways in which an IPv6 interface identifier is
determined:
 A 64-bit interface identifier that is derived from the Extended
Unique Identifier (EUI)-64 address. The 64-bit EUI-64 address is
defined by the Institute of Electrical and Electronic Engineers
(IEEE). EUI-64 addresses are either assigned to a network
adapter or derived from IEEE 802 addresses. This is the default
behavior for IPv6 in Windows XP and Windows Server 2003.
 As defined in RFC 3041, it might have a temporarily assigned,
randomly generated interface identifier to provide a level of
anonymity when acting as a client.

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IPv6 Interface Identifiers
 As defined in RFC 2472, an interface identifier can be
based on link-layer addresses or serial numbers, or
randomly generated when configuring a Point-to-Point
Protocol (PPP) interface and an EUI-64 address is not
available.
 It is assigned during manual address configuration.
 It is a permanent interface identifier that is randomly
generated to mitigate address scans of unicast IPv6
addresses on a subnet. This is the default behavior for
IPv6 in Windows Vista and Windows Server “Longhorn.”
You can disable this behavior with the netsh interface
ipv6 set global randomizeidentifiers=disabled
command.

IPv6 Addressing 42
EUI-64 address-based
interface identifiers

43
IPv6 Modified EUI-64 Format
 Stateless autoconfiguration is a mechanism that
allows nodes on a network to configure their IPv6
addresses themselves without any intermediary
device, such as a DHCP server.
 The link-local address and stateless
autoconfiguration are functions of IPv6 that
automatically expand the Ethernet MAC address
based on a 48-bit format into a 64-bit format (EUI-
64).
 The conversion from 48-bit to 64-bit is a two-step
operation.

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The IPv6 Modified EUI-64 Format
 It is essential that all devices on the same network use the same
mapping technique
 The most common type of layer 2 addresses are IEEE 802 MAC
addresses.
 Layer 2 addresses= 48 bits, arranged into two blocks of 24.
 Upper 24 bits = organizationally unique identifier (OUI), with
different values assigned to individual organizations
 Lower 24 bits = device identifier

 EUI-64 Format
 It is similar to the 48-bit MAC format, except that while the OUI
remains at 24 bits, the device identifier becomes 40 bits instead
of 24.
 This provides gives each manufacturer 65,536 times as many
device addresses within its OUI.

IPv6 Addressing 45
Converting 48-Bit MAC Addresses to
IPv6 Modified EUI-64 Identifiers

IPv6 Addressing 46
IPv6 Address with an Embedded
IPv4 Address
 IPv4-compatible IPv6 address is a special unicast IPv6 address
used by transition mechanisms on hosts and routers to automatically
create IPv4 tunnels to deliver IPv6 packets over IPv4 networks.
 Address is made up of six high-order fields of 16-bit hexadecimal
values, represented by X characters, followed by four low-order
fields of 8-bit decimal values (IPv4 address), represented by d
characters (for a total of 32 bits).

IPv6 Addressing 47
IPv6 Address with an Embedded
IPv4 Address
 Two kinds of IPv6 addresses have an embedded IPv4
address:
1. IPv4-compatible IPv6 address
 Used to establish an automatic tunnel to carry IPv6 packets over
IPv4 networks.
 related to a transition mechanism of the IPv6 protocol .
2. IPv4-mapped IPv6 address
 Used only on the local scope of nodes having both IPv4 and IPv6
stacks.
 Nodes use IPv4-mapped IPv6 addresses internally only.
 These addresses are never known outside the node itself and
should not go on the wire as IPv6 addresses.

IPv6 Addressing 48
IPv6 Address with an Embedded
IPv4 Address
IPv4-compatible IPv6 address

IPv4-mapped IPv6 address

IPv6 Addressing 49
IPv6 and Subnetting
 The only acceptable form to represent a network
mask in IPv6 is CIDR notation.
 Although IPv6 addresses are in hexadecimal format,
the network mask value is still a decimal value.

IPv6 Addressing 50
51