nanog mailing list archives
Re: BGP Path Filtering
From: "Stephen J. Wilcox" <steve () telecomplete co uk>
Date: Fri, 16 May 2003 10:01:16 +0100 (BST)
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 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.
yes it will
Next up is: ip as-path access-list 3 permit ^12345_[0-9]$* Which seems correct to me. Is this still best practice (or even correct)?
no, perhaps you mean ..[0-9]*$ but that still wont allow multiple prepends as it wont match the space only the numbers try ip as-path access-list 3 permit ^(_12345_)+$ which will allow one or more of their as's ASN is pretty crude tho, consider using a prefix list to filter each prefix and include length Steve
Mark Radabaugh Amplex (419) 720-3635
Current thread:
- Re: Communities BCP [was: RE: BGP Path Filtering], (continued)
- Re: Communities BCP [was: RE: BGP Path Filtering] Danny McPherson (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Stephen J. Wilcox (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Danny McPherson (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Richard A Steenbergen (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Guy Tal (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Leo Bicknell (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Danny McPherson (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Danny McPherson (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Stephen J. Wilcox (May 16)
- Re: Communities BCP [was: RE: BGP Path Filtering] Guy Tal (May 16)
- Re: BGP Path Filtering Leo Bicknell (May 16)
- Re: BGP Path Filtering Sean Donelan (May 16)
- Re: BGP Path Filtering Leo Bicknell (May 16)
- Re: BGP Path Filtering Sean Donelan (May 16)
- Re: BGP Path Filtering Joe Abley (May 17)
- Re: BGP Path Filtering Iljitsch van Beijnum (May 17)
- Re: BGP Path Filtering Sean Donelan (May 17)