From: Bizzell, Keith (keith.bizzell@eds.com)
Date: Mon Aug 07 2006 - 18:17:04 ART
Here's the Cisco documentation:
http://www.cisco.com/univercd/cc/td/doc/product/atm/c8540/12_0/13_19/cmd
_ref/appc.htm
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Huizinga, Rene
Sent: Monday, August 07, 2006 4:03 PM
To: 'spycharlies@hotmail.com'; ccielab@groupstudy.com
Subject: RE: BGP regular expression
Hi Utoya,
It's quite simple.
The '^' sign stands for 'start of the line', so that character
identifies that the characters after should only match if that line
start with it...
The '_' sign is the equivalent to a seperator (e.g. space) between 2
entries, OR the end-of-line.
The '$' sign stands for 'end of line', so the opposite of the '^'. All
characters before that sign will match if it's the end of the line...
Further, the reg-exp. Matches the AS-Path line where the last, most
recent one, connecting to your AS, is at the left hand side in the line
and the originating AS is at the right hand side.
So the '^300_' matches an AS-path matching prefixes advertised by AS300,
regardless of the AS-path length. If the path-length is 1, it's
originated within AS300, if it's 2 then in an AS with which AS300
directly peers, if longer then deeper in the path by a later AS...
The '^300$' will only match prefixes advertised AND originated within
AS300, since it states that the advertisement should be from AS300 and
having an AS-path length of 1 only...
One which is often used as well would be e.g. '_300$'. This matches all
prefixes originated within that AS, regardless of the path-length or by
whom advertised...
If you do a search on the Cisco-site for the BGP regular expressions
you'll find one or more nice documents giving an overview of all
reg-expr's Cisco supports, together with some samples...
Cya
Rene.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
spycharlies@hotmail.com
Sent: Monday, August 07, 2006 10:43 PM
To: ccielab@groupstudy.com
Subject: BGP regular expression
Hey Guys
I was wondering wat the differences btw these 2 commands are, they seems
to be doing thesame thing (* prefixes learned from AS300)
ip as-path access-list 1 permit ^300_
and
ip as-path access-list 1 permit ^300$
cheers
Uyota
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