[154924] in North American Network Operators' Group
Re: using "reserved" IPv6 space
daemon@ATHENA.MIT.EDU (Jimmy Hess)
Tue Jul 17 01:11:21 2012
In-Reply-To: <1342500058.6281.154.camel@karl>
Date: Tue, 17 Jul 2012 00:10:50 -0500
From: Jimmy Hess <mysidia@gmail.com>
To: Karl Auer <kauer@biplane.com.au>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 7/16/12, Karl Auer <kauer@biplane.com.au> wrote:
> I think Oliver meant the subnet router anycast address.
> Anycast gets you to one-of-many. The routers work out which of them is
Just to reaffirm that. Rfc 4291 states packets sent to the
subnet-router anycast will be delivered to one router on the subnet.
That's fine for traffic with a destination IP of the anycast
address; they'll land on one of the routers, and perhaps one of the
routers will respond.
But what about packets with a destination address on another network
and trying to use the anycast address as a 'gateway'? The
destination IP in the IP packet header of the forwarded packet won't
be the anycast address; the last known hardware address for the IP,
if it's unicast, may be down, so it's probably nonsensical to enter
an anycast address as default gateway, unless using the subnet
anycast address as a router/gateway has special behavior defined
elsewhere?
RFC 4291 S2.6.1
http://tools.ietf.org/html/rfc4291
"
Packets sent to the Subnet-Router anycast address will be delivered
to one router on the subnet. All routers are required to support the
Subnet-Router anycast addresses for the subnets to which they have
interfaces.
"
--
-JH
