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Re: Implementations/suggestions for Multihoming IPv6 for DSL sites
From: Mark Andrews <marka () isc org>
Date: Fri, 08 Apr 2011 11:34:37 +1000

In message <4D9E27A5.3040108 () forthnet gr>, Tassos Chatzithomaoglou writes:

Michel de Nostredame wrote on 07/04/2011 22:30:
On Thu, Apr 7, 2011 at 2:27 AM, Daniel STICKNEY<dstickney () optilian com>  wr
I'm investigating how to setup multihoming for IPv6 over two DSL lines
(different ISPs), and I wanted to see if this wheel has already been
invented. Has anyone already set this up or tested it ?
When you talking about "two DSL lines", I assume this is mainly for
office / residential environment to have redundancy and/or increase
uplink availability.

In this environment, BGP exchanges with uplink ISPs for multihoming
usually is not an option. One reason maybe cost, another reason maybe
ISP doesn't like to setup BGP with a DSL customer. At least in my
case, reason #2 always prevent my customers to setup BGP with uplink

As Seth pointed out SHIM6 is still an academic exercise, my
experiences to resolve this needs at this moment is leveraging NAT66,
as what we did in IPv4 world. I use FreeBSD+PF and Juniper
NetScreen/SSG to do NAT66 in several different locations, and they all
works as expected so far.

Some people don't like NAT especially NAT66, but to be realistic that
does work, and works well in terms of providing redundancy over two
DSL lines for office / residential needs.


Although i generally hate NAT, multihoming must be the only (or at least 
the most important) reason why NAT66 has to be standardized.
Otherwise some kind of routing must be implemented on hosts.

And what's wrong with routing on hosts?  If a router advertises a
prefix it should know where to send traffic that originates from
that prefix.  You just choose the next hop by looking at which
routers are advertising the prefix for the source address for this
packet and choosing between them.  It's a touch more state to be
kept with every address.  It would also be useful for filtering out
rouge RAs.  You look at the address you learnt the prefix from then
filter out that router / prefix.


Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka () isc org

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