Re: BGP Path Filtering

[Jay Ford <jay-ford () uiowa edu>]

On Thu, 15 May 2003, Mark Radabaugh wrote:
> I'm having a hard time finding best practices for filtering outbound bgp
> announcements when providing transit to bgp-speaking customers.  While we
> currently multi-home to several providers it appears we will soon need to
> provide transit for customers with their own AS's.

I like using BGP communities:
   o  filter announcements you receive from downstreams based on your
      criteria of choice
   o  set a specific BGP community (yourAS:whatever) on announcements which
      are to be propagated to various places (upstream providers, etc.)
   o  do output filtering based on the communities you set
Make sure you clear yourAS:whatever in announcements from your BGP peers.

You can use this same technique for prefixes you originate, so that all your
outbound BGP filtering is based on communities.

________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: jay-ford () uiowa edu, phone: 319-335-5555, fax: 319-335-2951