From: Carley, Charles (charlesc@xxxxxxxxxx)
Date: Mon Jun 03 2002 - 09:26:27 GMT-3
Have you tried using no-export communities to accomplish this?
-----Original Message-----
From: Dustin.Yates@ercgroup.com [mailto:Dustin.Yates@ercgroup.com]
Sent: Sunday, June 02, 2002 11:56 PM
To: ccielab@groupstudy.com
Subject: AS-Path Filter with Confederation
I'm trying to filter routes sent to an EBGP neighbor to prevent the local AS
from being used as a transit AS. The classic example allows for you to use
an as-path filter with ^$ as the regular expression on the outgoing filter
list. What if the AS is a confederation with multiple sub-AS's?
>From the 'sh ip bgp' command below, I want to filter routes I send to my
neighbor at AS 130. Only one route is a candidate for filtering that is
originated in AS 1000:
R6#sh ip bgp
BGP table version is 11, local router ID is 155.10.6.6
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 155.10.0.0/24 155.10.135.3 20 100 0 (250) i
*> 155.10.25.0/24 155.10.5.5 0 100 0 (250) i
*> 155.10.44.0/24 155.10.45.4 6892 100 0 (250) i
*> 155.10.139.0/24 155.10.135.3 58 100 0 (250) i
*> 198.6.48.0/21 155.10.2.2 100 0 (250 8) i
*> 198.6.53.0 155.10.2.2 0 100 0 (250 8) 1000 i
***This is the route I want to filter***
Ok, a couple of sample 'sh ip bgp regexp' commands shows that I can't filter
this route with a simple expression:
R6#sh ip bgp regexp 8
BGP table version is 11, local router ID is 155.10.6.6
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 198.6.48.0/21 155.10.2.2 100 0 (250 8) i
*> 198.6.53.0 155.10.2.2 0 100 0 (250 8) 1000 i
R6#sh ip bgp regexp 250
BGP table version is 11, local router ID is 155.10.6.6
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 155.10.0.0/24 155.10.135.3 20 100 0 (250) i
*> 155.10.25.0/24 155.10.5.5 0 100 0 (250) i
*> 155.10.44.0/24 155.10.45.4 6892 100 0 (250) i
*> 155.10.139.0/24 155.10.135.3 58 100 0 (250) i
*> 198.6.48.0/21 155.10.2.2 100 0 (250 8) i
*> 198.6.53.0 155.10.2.2 0 100 0 (250 8) 1000 i
R6#sh ip bgp regexp ^$
R6#sh ip bgp regexp ^250$
R6#sh ip bgp regexp ^250 8$
R6#sh ip bgp regexp ^(250 8)$
R6#
My goal is to filter this with a generic statement such as ^$. Or, even one
that would use the confederation peers (in this case 250, 8, & 6). The
confederation id is 22. What is the trick to getting this route to filter
as part of a generic outgoing filter list-- without targeting specific
external AS's such as AS 1000? I know there are other ways to do this, but
I'm trying strictly to do this with an as-path filter. Pointers to CCO
documents that address path filters with confederations such as this would
be greatly appreciated.
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