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  • 1.  BGP path prepend using communities

    Posted 06-08-2011 05:54

    Hi All,


    I am trying to set up a bgp community so that if a bgp transit customer uses it, it will automatically prepend the AS x amount of times. it best to prepend my AS ( which i have managed to write a policy for ) or is there a way with a regexp to add his AS to the prepend?


    Any thoughts/suggestions much appreciated.



  • 2.  RE: BGP path prepend using communities
    Best Answer

    Posted 06-08-2011 06:51



    There's a very flexible way, using predefined(customer independent) communities and as-path-expand statement.

    The point is that the AS number of your peer (from which the prefix you have received) will be prepended, not the AS number of the originating AS. 


    community prepend-1 65000:1; 

    community prepend-2 65000:2;


    policy-statement prepend { 
    term prepend-1 { 
    from community prepend-1; 
    then as-path-expand last-as; 

    term prepend-2 { 
    from community prepend-2; 
    then as-path-expand
     last-as count 2; 

  • 3.  RE: BGP path prepend using communities

    Posted 06-09-2011 00:29

    Hi Dumitru,


    Thats exactly what I'm looking for.  Thanks so much!