From: Geert Nijs (geert.nijs@simac.be)
Date: Mon Jun 14 2004 - 13:03:54 GMT-3
The regular expression to match AS 100 and any directly connected AS,
including AS-path-prepending is:
^100(_100)*(_([0-9]+)(_\3)*)?$
Regards,
Geert
-----Oorspronkelijk bericht-----
Van: nobody@groupstudy.com [mailto:nobody@groupstudy.com] Namens
Alexander Arsenyev (GU/ETL)
Verzonden: maandag 14 juni 2004 16:13
Aan: ccielab@groupstudy.com
Onderwerp: RE: AS PATH
Actually (10)+ in Cisco regexp means 10 or 1010, not 10_10_10_... Please
remember that AS number is 2 bytes long so there is no such thing as
AS 101010.
To match neighbor AS number with prepends and its direct customers (no
prepends) use ^(AS#_)+[0-9]*$ I've tried to develop AS path regexp which
matches neighbor AS with prepends and its direct customers with prepends
but no luck so far. The trick is that this regexp should match only 2
different AS numbers in AS Path while ([0-9]+_)* matches ANY number of
different AS numbers in AS path because regexp are "greedy" (I think).
HTH,
Cheers
Alex
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Scott Morris
Sent: 12 June 2004 14:36
To: 'Richard Dumoulin'; ccielab@groupstudy.com
Subject: RE: AS PATH
If you want to take into account the pre-pending of an ACL, you would
associate the "+" character, which is "one or more of the preceding
value". Don't forget to create a character class though with ().
If you put 10+ by itself, that only treats the "0" as "one or more", so
10, 100, 1000, 10000 would match.
If you do (10)+ that will treat "10" as the thing to repeat. So whether
my as-path has 10 or 10 10 10 10 10 doesn't matter.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
CISSP, JNCIP, et al. IPExpert CCIE Program Manager IPExpert Sr.
Technical Instructor swm@emanon.com/smorris@ipexpert.net
http://www.ipexpert.net
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Richard Dumoulin
Sent: Saturday, June 12, 2004 9:19 AM
To: 'ccielab@groupstudy.com'
Subject: AS PATH
Some time ago, someone posted a link where an example of as-path
access-list which embraced a neighbor AS plus its directed customers was
shown.
This acl did take into account prepending from those AS's.
If anyone conserves this post would he send it again please ? I 've
searched the archives but in vane,
Thanks
--Richard
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