How to modify an AS path for BGP routes

[TCC_2]

Core Issue

The only global Border Gateway Protocol (BGP) metric available to influence the best path selection is the Autonomous System (AS) path length.

Resolution

To prepend an arbitrary AS path string to BGP routes, issue the set as-path prepend command. 

This example prepends 100 100 100 to all the routes advertised to 10.108.1.1:

route-map set-as-path 
 match as-path 1 
 set as-path prepend 100 100 100 
! 
router bgp 100 
 neighbor 10.108.1.1 route-map set-as-path out 

For more information, refer to the set as-path section of BGP Commands.