[23661] in North American Network Operators' Group
RE: Cisco Route filtering [was Re: OPS: BGP spew from ASN 7374]
daemon@ATHENA.MIT.EDU (Martin, Christian)
Thu Apr 8 19:17:46 1999
From: "Martin, Christian" <CMartin@mercury.balink.com>
To: "'alex@nac.net'" <alex@nac.net>
Cc: "'nanog@merit.edu'" <nanog@merit.edu>
Date: Thu, 8 Apr 1999 19:16:15 -0400
Errors-To: owner-nanog-outgoing@merit.edu
> I've had a question on this for some time that maybe can get answered
> here.
>
> Let's assume for a moment that I have a network of 209.123/18
> (1/4 of a
> classful B).
>
> Let's further assume that my upstream filters me with:
>
> access-list 2002 permit ip host 209.123.0.0 host 255.255.0.0
> neigh 2.3.4.5 distrib 2002 in
>
> Will my /18 announcement make it through this /16 filter?
No. The ACL specifies an exact match.
> Would the same be true with a prefix-length filter, which I assume the
> syntax would be:
>
> ip prefix-list 1 permit 209.123.0.0/16
> neigh 2.3.4.5 prefix-list 1 in
>
Same deal.
Chris
