10-15-2007 09:59 AM - edited 03-03-2019 07:10 PM
I was looking over a router config when I ran across the following:
ip as-path access-list 17 permit ^[0-9]+$
ip as-path access-list 17 permit ^$
what is the meaning of this I tried looking it up but maybe I'm not understanding what I read....sorry for the silly question
Thank you warren
10-15-2007 10:03 AM
Warren-
Not a silly question! I won't give you the answer directly, but take a look here to figure it out.
http://www.cisco.com/warp/public/459/bgp-toc.html#asregexp
What you see are regular expressions that are used to filter AS's in BGP.
HTH and please rate.
10-15-2007 10:54 AM
(ip as-path access-list 17 permit ^$) is used for bgp updates sent to peers.
There should be a router bgp route-map associated with this.
Means all networks originating from your AS and no others, protects your AS from becomming a transit-as.
The other command, I'm not exactly sure, have to do the math.
10-15-2007 11:23 AM
Hi,
the statement ^[0-9]+$ will match bgp routes originated from next upstream ....that's with AS-path length 1 , the next statement ^$ is will match the routes originated by the router... So The as-path 17 will be a summary of routes originated from next upstream and routes originated by the router
Regards,
Haris
10-16-2007 08:38 AM
Thank you all for the info it was very helpfull and thank you Haris for the explaination!!!
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