IPv6 multihoming

George Bonser gbonser at seven.com
Fri Feb 4 18:56:52 CET 2011

> I'm just curious because it seems that there is nothing "official" or
> best pratice, so this will break if some ISPs decides to filter on /32
> or something.
> What's your take on this?
> /Roger

Announcing a /48 from PA space might be difficult for a while but from
PI space should be ok.  The problem is going to be dual-stacked routers.
Because of fragging of the v4 space after runout, we are going to see
growth in both the v6 and v4 tables at the same time.  A v6 route takes
anywhere from 2x to 4x the resources of a v4 route.  People are going to
want to keep the number of v6 routes down until either the v4 table
begins to shrink or they go dedicated stack.  Some might tighten up on
v4 multihoming, though, and stop accepting smaller than /24

Actually, thanks for sending this email.  It caused me to look at my BGP
tables and I see one upstream announcing a boatload of /32s with BGP
even though it is part of a /27 (and a /29!) they also announce to me
that I get from no other upstream.  Looks like I need to clamp down on
some filters for that upstream.  Looks like they are sending me over
2500 /32s by BGP.

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