An anycast address has the same format as a unicast address, however on a network different hosts can have the same address on their interfaces, these interfaces MUST be configured as anycast.
As unicast can be thought of as one-to-one, multicast as one-to-many, anycast is ono-to-one-of-many. What this means is a packet sent to an anycast address will be routed to the closest (as in routing cost) host.
anycast is a router concept; of the available pool of unicast destinations for a particular address, some upstream router will eventually pick the "nearest" one by some criterion, and the unicast packet ends up at that specific host. Different clients from different originating LAN's could end up at different destinations if they take different paths through the routers.
In general, anycast is used with hosts which are on different LAN's, no two on-link with each other. A typical use is to increase redundancy for DNS servers. The soon to be deprecated IPv6 6to4 relays also share anycast address 220.127.116.11/24 on the v4 side. Anycast is not a v6-specific concept; it can be done with both v4 and v6.
Having the same IPv6 unicast address assigned to multiple interfaces would tend to result in duplicate address detection failures, either on-host or on-link.
An anycast address is best thought of as a single address that will get you to the nearest server offering a specified service. For example, one of the DNS root servers, F Root, is in fact about over 50 servers in locations worldwide (http://www.isc.org/f-root/). However, for the purposes of DNS access (not for maintanence; they each have an individual address for purposes that require them to be individual machines), they each use the same two addresses: F-root answers queries over IPv4 on 18.104.22.168, and over IPv6 on 2001:500:2f::. When you send a DNS request to one of those two addresses, it goes to whichever of the two happens to be online at the time and, from a routing perspective, nearest to you.
This document gives several answers on frequently asked questions for PFRv3 channel state behavior.
Q1: What are all the channel operational states from a BR (border role) perspective and what are the rules/conditions to be in each st...
The need was to reach an host inside a LAN through a VPN connection managed by the LAN gateway (Cisco 1921).
The LAN gateway performs NAT and there was a dedicate nat rule for the host i wanted to reach through VPN.
I couldn't connect to the hos...
We have 3 identical switches configured by someone else and would like to claim some of the Gigabit ports(G1/G2/G3/G4) for use on servers. When we try to change the wiring and configuration, we run in to connectivity issues. Attached is a des...