Anycast address – Cisco ASA 5505 User Manual

Page 1891

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B-9

Cisco ASA 5500 Series Configuration Guide using the CLI

Appendix B Addresses, Protocols, and Ports

IPv6 Addresses

Figure B-1

IPv6 Multicast Address Format

IPv6 nodes (hosts and routers) are required to join the following multicast groups:

The All Nodes multicast addresses:

FF01:: (interface-local)

FF02:: (link-local)

The Solicited-Node Address for each IPv6 unicast and anycast address on the node:
FF02:0:0:0:0:1:FFXX:XXXX/104, where XX:XXXX is the low-order 24-bits of the unicast or
anycast address.

Note

Solicited-Node addresses are used in Neighbor Solicitation messages.

IPv6 routers are required to join the following multicast groups:

FF01::2 (interface-local)

FF02::2 (link-local)

FF05::2 (site-local)

Multicast address should not be used as source addresses in IPv6 packets.

Note

There are no broadcast addresses in IPv6. IPv6 multicast addresses are used instead of broadcast
addresses.

Anycast Address

The IPv6 anycast address is a unicast address that is assigned to more than one interface (typically
belonging to different nodes). A packet that is routed to an anycast address is routed to the nearest
interface having that address, the nearness being determined by the routing protocol in effect.

Anycast addresses are allocated from the unicast address space. An anycast address is simply a unicast
address that has been assigned to more than one interface, and the interfaces must be configured to
recognize the address as an anycast address.

The following restrictions apply to anycast addresses:

An anycast address cannot be used as the source address for an IPv6 packet.

92617

128 bits

4 bits

4 bits

0 if permanent
1 if temporary

Interface ID

0

1111 1111

8 bits

8 bits

F

F

Flag

Scope

Flag

=

Scope =

1 = node
2 = link
4 = admin
5 = site
8 = organization
E = global

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