Apologies for previous message but it was incomplete!!
Hi
As regards the symbols:
^ - Beginning Of String,
$ - End Of String,
_ - Any Delimeter (beginning, end, whitespace, tab, comma),
. - Any Single Character,
+ - matches one or more atoms,
? - matches zero or one atom,
* - matches zero or more atoms,
() - Can be used to group smaller regular expressions into larger
expressions
Note atom => Sequence
With reference to your access-lists:
ip as-path access-list 1 permit ^$
Here you are permitting IP addresses generated in your AS
ip as-path access-list 4 permit ^(_6774) +$
Permit AS 6774. It does not have to be at the start, but it cannot be at
the end.
ip as-path access-list 10 permit .*5413$
This permits AS5413 provided IP's are generated in this AS, due to the $
sign just after the AS number, but which are also passing through another
AS, due to the .
ip as-path access-list 6 permit ^ (_3414) + (_2423) +$
Permit traffic going through AS3414 and AS2423. The traffic is not
generated in these AS's
Hope that this helps. As regards links, these are quite good:
http://joe.lindsay.net/bgp.html
http://www.cisco.com/pcgi-bin/tablebuild.pl/techdoc
http://www.cisco.com/warp/public/459/13.html
http://www.cisco.com/warp/public/459/14.html
http://www.cisco.com/warp/public/459/15.html
http://www.cisco.com/warp/public/459/16.html
http://www.cisco.com/warp/public/459/17.html
http://www.cisco.com/warp/public/459/18.html
Regards
Geoffrey
----- Original Message -----
From: Andre Fecteau
Newsgroups: groupstudy.cisco
To: [EMAIL PROTECTED]
Sent: Wednesday, November 22, 2000 7:13 PM
Subject: BGP as-path access-lists
Hello,
I have been recently placed in the awkward position of making some changes
to our BGP configuration. The problem is that I understand how bgp works
for the main part, but I don't have any information on the meaning of the
symbols used in the following as-path access-lists (^, $, _, ., +, (), *).
Could someone tell me what each of them mean? Could someone also point me
to a Cisco page that explains them in detail? I have been searching and
cannot find anything except examples that include these symbols.
Unfortuneately these examples have not helped my understanding. I have a
good idea as to what they probably mean, but I need to know their exact
meaning. It is difficult to manage something you don't have a clear
understanding of!
ip as-path access-list 1 permit ^$
ip as-path access-list 4 permit ^(_6774) +$
ip as-path access-list 10 permit .*5413$
ip as-path access-list 6 permit ^ (_3414) + (_2423) +$
HELP!!!
Andre
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