Excuse me for responding myself here. Just like to clarify my previous message a bit. The note below does not intend to solve Randy's problem for his chosen policy. It rather intends to describe a different policy used by many ISPs which won't run into the same problem. IMO, ISPs who are engaging in the 'hot potato' routing practice have the obligation to announce consistent routes to its peers at different peering points. It may require an ISP to change it's internal policy to achive this with reasonable maintance work (like the one described below) or to excercise whatever internal policy it decide but do more work (configuration management,etc) to fulfill the obligation. --Jessica speaking for myself. Date: Fri, 14 Mar 1997 12:48:49 EST To: jgs@ieng.com cc: vaf@valinor.barrnet.net, Sean Donelan <SEAN@sdg.dra.com>, nanog@merit. ***edu From: Jessica Yu <jyy@ans.net> Subject: Re: consistent policy != consistent announcements Return-Path: owner-nanog@merit.edu Sender: owner-nanog@merit.edu Content-Type: text Content-Length: 5173 If a provider/AS does not have the policy of dumping hot potatos to other peers for the traffic to its customers who happen to multihome to those peers. Then there is a simple way to do it. They can have policy of always favor its own customer routes over the routes learned from other peers. This will avoid the inconsistent announcement by eliminating the cases that some part of the AS favors routes M from it's customer and other part favors M from another peer, thus announce consistent routes to other peers. It's very easy to manage this policy. Just assign lower (less favored) local_pref to routes learned from peers than those learned from customers. It's AS based. By using the default local_pref value, one only need to assign a lower than default local_pref value to the peer AS at border routers. A good side effect of this policy is that your customers routes will be protected from being blackingholed from careless ISPs leaking/advertising your customers routes but have no way to reach them. --Jessica