On 10/01/2014 07:45, John Levine wrote: >>> It looks like the sites John talked to are multihomed, NOT doing >>> routing at their edge (??), and yet wanting to filter? I don't think >> that's not clear, from john's description at least. > > I can ask (the meeting's not over yet) but I gather that these are > multihomed customers who don't do BGP. The ISP knows what ranges it's > routing to the customer, but it doesn't know what ranges are routed to > the same customer by someone else. This is not a new problem; we certainly discussed it in the multi6 WG ten years ago: http://tools.ietf.org/html/draft-huitema-multi6-ingress-filtering-00 Actually it's one of the reasons that multi6 led to shim6, which mainly avoids this problem (but is disliked by ISPs for other reasons). Brian