BGP Path Filtering
Niaz, Wajahat
Wajahat.Niaz at dsl.net
Fri May 16 03:16:44 UTC 2003
You should start using communities if you want to provide transit to
downstream bgp customers. Use the right tool for the right job.
Ali,
DSL.net, Inc.
-----Original Message-----
From: Mark Radabaugh [mailto:mark at amplex.net]
Sent: Thursday, May 15, 2003 10:29 PM
To: nanog at merit.edu
Subject: BGP Path Filtering
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 find lots of references (and understand) the basic
ip as-path access-list 3 permit ^$
and it would seem that should we wish to provide transit for a bgp customer
AS12345 we would use:
ip as-path access-list 3 permit ^12345$
but I think this breaks if AS12345 prepends their advertisement.
Next up is:
ip as-path access-list 3 permit ^12345_[0-9]$*
Which seems correct to me. Is this still best practice (or even correct)?
Mark Radabaugh
Amplex
(419) 720-3635
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