RE: BGP Filtering

From: Timothy Chin (tim@1c-solutions.com)
Date: Sun Mar 22 2009 - 14:45:13 ART


You would most likely use ^ASXX$ if your AS was directly connected to
the AS in question. You would use _ASXX$ if you weren't directly
connected.

Tim

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Cisco Fanatic
Sent: Sunday, March 22, 2009 1:41 PM
To: ccielab@groupstudy.com
Subject: BGP Filtering

Hi All,

If we have to learn only those prefixes that Originate in some AS ASXX.
We can
use ^$ and _XX$. In some workbooks I have seen one or the other being
used. I
have tested both and both are working (the way it should). Which one is
better
over the other.

For example,
!
router bgp XX
 neighbor x.x.x.x filter-list 10 in
!
ip as-path access-list 10 deny _ASXX$
ip as-path access-list 10 permit .*
!
*******************************************
Or/And,

!

router bgp XX

 neighbor x.x.x.x filter-list 10 in

!

ip as-path access-list 10 deny ^ASXX$
!
*******************************************

Yuri



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