[58484] in North American Network Operators' Group
BGP Path Filtering
daemon@ATHENA.MIT.EDU (Mark Radabaugh)
Thu May 15 22:29:53 2003
From: "Mark Radabaugh" <mark@amplex.net>
To: <nanog@merit.edu>
Date: Thu, 15 May 2003 22:29:18 -0400
Errors-To: owner-nanog-outgoing@merit.edu
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
