Configuring an IPv6 anycast address on an interface

In IPv6, an anycast address is an address for a set of interfaces belonging to different nodes. Sending a packet to an anycast address results in the delivery of the packet to the closest interface configured with the anycast address.

An anycast address looks similar to a unicast address, because it is allocated from the unicast address space. If you assign an IPv6 unicast address to multiple interfaces, it is an anycast address. On the device, you configure an interface assigned an anycast address to recognize the address as an anycast address.

For example, the following commands configure an anycast address on interface 1/2/1.

device(config)# interface ethernet 1/2/1
device(config-if-e1000-1/2/1)# ipv6 address 2001:DB8::/64 anycast

IPv6 anycast addresses are described in detail in RFC 1884. Refer to RFC 2461 for a description of how the IPv6 Neighbor Discovery mechanism handles anycast addresses.