From: Scott Morris (swm@emanon.com)
Date: Fri Sep 26 2008 - 10:13:06 ART
So if you are looking to AS Y, the first question I have is whether Y is you
or not?
So if YOU are AS 100, and AS Y is 200, then you would be looking at one as
path (predictable due to the idea that you know who is directly peered with
yourself) and one MORE ASN (unpredictable, but only 1.
So ^200_[0-9]+$ would cover your neighbor and one other.
^200_([0-9]+)?$ would cover your neighbor and UP TO one other.
^(_200)(\1)*(_[0-9]*)(\3)*$ would cover your neighbor and UP TO one other,
but allow prepending of either ASN.
The \# part allows the 'x' # parenthetical to be repeated.
HTH,
Scott Morris, CCIE4 #4713, JNCIE-M #153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
Senior CCIE Instructor
smorris@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Outside US: 775-826-4344
Knowledge is power.
Power corrupts.
Study hard and be Eeeeviiiil......
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Peter Hauck
Sent: Friday, September 26, 2008 2:23 AM
To: ccielab@groupstudy.com
Subject: Correct AS Path
For those who have done this in IE it may be familiar....
Create an AS filter to filter prefixes originated by AS Y's directly
connected customers. (Assumning you are on the router that is part of ASY).
Would this mean ^[0-9]+$ or ^([0-9]+)?$
I am thinking that the first AS-PATH as it matches what is specified, as the
second also allows routes from the AS itself.
Am I wrong?
-- PeterBlogs and organic groups at http://www.ccie.net
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