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ISP Filter Policies--Effect is what?
I'm trying to figure out to what degree the existence of these policies should be accounted for in a BGP design which includes sites around the world. I've read through a few of the threads having to do with Verio's Filtering Policy. And I read the policies listed here: http://www.nanog.org/filter.html Consider the following theoretical scenario: Site BGP Advertisement to ISP Amsterdam 18.104.22.168/24 AMSISP Austin 22.214.171.124/24 Genuity & Internap SanFran 126.96.36.199/24 Genuity & Internap Tokyo 188.8.131.52/24 TOKISP Sydney 184.108.40.206/24 SYDISP 1. Since Verio says they would not accept /24 nets drawn from Class B space, I assume this means that they don't insert a /16 into their tables so that the /24 nets appear to Verio customers as unreachable. In this case, a design that wants to extend connectivity to verio customers (and any other ISP with similar policies) must include a /16 advertisement from at least one of the sites. 2. Suppose a customer of a Verio-like ISP, wishes to go to ftp. foo.org. DNS returns 220.127.116.11 (in amsterdam, see above). Verio passes the traffic to the neighbor it received the /16 advertisement from. At this point, the best thing that could happen is if that neighbor has the /16 and /24 networks in its route table, right? That means, a path exists for that user to the amsterdam server and the only problem with routing to Amsterdam is that Verio possibly handed the traffic to a sub-optimal neighbor. Am I understanding this issue correctly? I'm new to BGP. I've tried to get a handle on this issue on my own and by working with Genuity, Internap and Cisco. No disrespect to those companies but each of them had this vague memory of Verio's policy but couldnt really tell me in plain language how it might affect the above scenario. Obviously, I wasn't talking to chief engineers. Someone from the CCIE mailing list suggested I browse the archives of this list, which I did. But I didnt find a clear enough answer to my questions--perhaps because they are too basic to be discussed here or I'm not good at using this lists archive search engine. Either way, any guidance on the above scenario is greatly appreciated. -BM