From: Pekka Savola [mailto:pekkas@netcore.fi]

When discussing RPF towards peers or w/ asymmetric paths, I'd recommend to read RFC 3704

I have, this is a very good document.

If your prefix filter stops a neighbor from advertising a prefix, maybe you would have to revise your prefix filtering policy (e.g., revise it more often, get notice if the peer sends you something you're filtering, tell to peers not to advertise anythnig that's not properly in the routing DB's, etc.)? This doesn't seem so bad to me...

I agree, but there are many people that think it is very bad. Trouble is, using RPF has a great potential for problems as it will drop traffic (which is the reason it's not being used in the first place). The point I was trying to make is as follows: if you don't use RPF (which is probably the case) then there is no harm in prefix-filtering peers (if you are not a tier-1) even if the prefix-filters are not perfect. Needless to say, there is no point prefix-filtering if your filters are completely messed up. Michel.