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Community Member

BGP AS-Path Prepend

How I can verify if BGP is applying AS-Path Prepend in the router that have the route-map?


Re: BGP AS-Path Prepend


afaik you can not. There are no show or debug commands providing this info. Only the receiving router allows you to check AS path prepending. In an internet environment you can try to see your BGP routes on route servers (f.e. has a collection of links).

Regards, Martin

Community Member

Re: BGP AS-Path Prepend

Are there another way to verify it (like a access-list).

Community Member

Re: BGP AS-Path Prepend


you can login into any route-server (e.g telnet and then do the traceroute for any of your ip can see the result...whether it is prepended or not and with the numbers it has been prepended.

hope this will help you.



Re: BGP AS-Path Prepend

Hi Aryan,

Please pardon my ignorance, but I would really be interested to know what is a Route-server and what all we can learn / access from that

Kind Regards,

Wilson Samuel

Community Member

Re: BGP AS-Path Prepend

A route server is simply a router that is publically accessible and has the full BGP route table on it. You can see a list of public route servers via this link.

Route servers are useful to view the BGP advertisements that other networks are receiving from you. You can log into a route server and view information about the subnets you are advertising, the preferred path back to you, along with other things. They are also helpful to be able to run traceroutes back to your network to see the chosen path.

If you search for route servers on Google you will get a ton more information.

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