On Jul 16, 2012, at 11:16 PM, Jimmy Hess wrote: > On 7/17/12, Karl Auer <ka...@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
NUD should actually take care of that. > 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. Yep. > 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. The whole concept of gratuitous arp is strictly IPv4. Owen
