[58485] in North American Network Operators' Group
RE: BGP Path Filtering
daemon@ATHENA.MIT.EDU (Niaz, Wajahat)
Thu May 15 23:17:48 2003
From: "Niaz, Wajahat" <Wajahat.Niaz@dsl.net>
To: 'Mark Radabaugh' <mark@amplex.net>, nanog@merit.edu
Date: Thu, 15 May 2003 23:16:44 -0400
Errors-To: owner-nanog-outgoing@merit.edu
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@amplex.net]
Sent: Thursday, May 15, 2003 10:29 PM
To: nanog@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
