IPv6 Anycast

Bernhard Schmidt berni at birkenwald.de
Wed Jun 2 15:01:29 CEST 2010

On Wed, Jun 02, 2010 at 02:43:43PM +0200, Martin Barry wrote:

> I'm trying to get a good grasp of IPv6 anycast.
> It appears to me that it's not quite analogous to the concept of anycast
> which has prevailed in IPv4 and has some deficiencies which would lead some
> operators to prefer to continue using the old method with IPv6 unicast
> addresses.
> Anyone read a good comparison of how the two match / differ?

IPv6 anycast is a special case of neighbor discovery where more than one
system can serve an address on a shared link. We use(d) that for
first-hop redundancy (shared address on two routers) back when HSRPv6
was not yet available.

Standard anycast like it has been done in IPv4 before (with
routingprotocols) is still possible and necessary, for example for
anycasted DNS deployments.


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