On Jan 9, 2014, at 7:09 AM, John R Levine <johnl(_at_)taugh(_dot_)com> wrote:
I was at a meeting talking to ops people from some large ISPs, who tell me
that when they tell their large customers about BCP 38, the customers say
forget it, because they're multihomed. I gather the situation is typically
that the customer has multiple address ranges, say from providers A and B.
Normally traffic from range A goes out through provider A, and vice-versa,
except sometimes when it doesn't. Sometimes it's failover, or it may be
deliberate asymmetic routing. The customers may not be running BGP, or if
they do, they don't want to announce range A to provider B for business
reasons I don't entirely understand but that are not going away.
The ISPs tell me that the customers are often ISPs themselves, so there are
lots of address ranges, far more than anyone could track manually even if
they wanted to.
I see BCP 84, which is now ten years old. The ISPs are aware of it, but it
doesn't seem to have done the trick. I can think of some hacks to
pseudo-announce ranges for filtering purposes, but surely I am not the only
person to have noticed this problem. What have people done to address this
issue?* I figure the first thing to do is to understand what's failed before.
There are some drafts you may find interesting:
http://tools.ietf.org/html/draft-boutier-homenet-source-specific-routing
http://tools.ietf.org/html/draft-troan-homenet-sadr
http://tools.ietf.org/html/draft-baker-ipv6-isis-dst-src-routing
http://tools.ietf.org/html/draft-baker-ipv6-ospf-dst-src-routing
http://tools.ietf.org/html/draft-baker-rtgwg-src-dst-routing-use-cases
http://tools.ietf.org/html/draft-xu-homenet-traffic-class
http://tools.ietf.org/html/draft-xu-homenet-twod-ip-routing
Homenet has been looking at this from the perspective of egress routing in
residential multihoming. I have been looking at it more from source/destination
routing in OSPF/IS-IS, for which "egress routing" and "residential multihoming"
are special cases.
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