using "reserved" IPv6 space

Tue Jul 17 06:16:32 UTC 2012

On 7/17/12, Karl Auer <kauer at biplane.com.au> wrote:
[snip
> I'm not sure I follow the logic there. If the anycast router changes the
> packet will be resent to the new subnet anycast router eventually
> (assuming some layer cares enough about the packet to resend it). The
> "last known hardware address" doesn't matter any more or less in this
> scenario than it does in any other routing situation.

The pertinent discussion is not about "any other routing situation";
it's about first hop redundancy.

The "last known hardware address" is in the NDP table, so the packet
retransmissions likely wind up in the same place

Another problem is the subnet anycast address may find unwanted
routers that have to listen on it, including routers with only one
interface and  incomplete routing info,  and including some
unauthorized   5-port   IPv6  router  someone smuggled into the
building and plugged in somewhere.

By contrast, a real  FHRP  that implements failover either uses a
virtual hardware address, or a 'gratuitous arp' type mechanism,  so
the packet retransmissions will go to the live failover partner.

--
-JH