IPv6 Anycast Address

IPv6 Anycast Address
An IPv6 anycast address is a global unicast address that is assigned to many interfaces in different
devices on the network. This means that this same network address is assigned to more
than one interface on the network. A packet that is sent to an anycast address will be delivered
to the closest interface with that anycast address. The closest interface is determined by the routing
protocol being used. Because anycast addresses are global unicast addresses, there is no way
to tell that a global unicast address is also an anycast address.
72 Chapter 2  IP Addressing
Therefore, any device configured with an anycast address will have to be configured explicitly
to recognize the address as an anycast address. You will never see traffic from an anycast address
because you cannot source IPv6 traffic using an anycast address; it is used only for destination
traffic. In fact, RFC 3513 suggested using anycast addresses only for routers—not end nodes—
until the complexities of their use could be determined in the real world.