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New Member

ip as-path

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

4 REPLIES

Re: ip as-path

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.

New Member

Re: ip as-path

(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.

Bronze

Re: ip as-path

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

New Member

Re: ip as-path

Thank you all for the info it was very helpfull and thank you Haris for the explaination!!!

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