[154933] in North American Network Operators' Group
Re: using "reserved" IPv6 space
daemon@ATHENA.MIT.EDU (Owen DeLong)
Tue Jul 17 02:47:20 2012
From: Owen DeLong <owen@delong.com>
In-Reply-To: <CAAAwwbV5Fnn0eJS2NXiigf2Lj7f3A9Dzu+gFjPZti4ja9BLLyg@mail.gmail.com>
Date: Mon, 16 Jul 2012 23:44:42 -0700
To: Jimmy Hess <mysidia@gmail.com>
Cc: NANOG List <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Jul 16, 2012, at 11:16 PM, Jimmy Hess wrote:
> On 7/17/12, Karl Auer <kauer@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
