[Xorp-users] BGP preference & as-path length

Marcel Prisi marcel-lists at virtua.ch
Fri Oct 13 02:52:31 PDT 2006

Hi all,

We are currently using openbgpd/openbsd as a core router for a small AS.
It works well but lacks an important feature we need.

We have two upstreams with different bandwidth, the one with the
smallest bandwidth has better routes, so close to all 
traffic goes through it, which is not optimal.

We already kind of solved inbound traffic using prepending &

We modified "local pref" for the outgoing traffic, but now all traffic 
goes through the other upstream, and nothing more through the smallest 
one, which is still not optimal.

What I need is to force some kind of discrimination so that smaller 
AS-paths go through one, and bigger through the other, so that I have an
arbitrary way to balance between the two upstreams.

Something like (pseudo config) 

ip as-path access-list 1 permit ^[0-9]+$ (one AS) 
ip as-path access-list 1 permit ^[0-9]+_[0-9]+$ (two AS's) 
ip as-path access-list 1 permit ^[0-9]+_[0-9]+_[0-9]+$ (three AS's) 
route-map CC-IN permit 10 
 match as-path 1 
 set local pref better (101?) 
route-map CC-IN permit 20 
 match bogon
 set local pref normal (100?) 

Is there a way to do something similar using xorp ???

Thanks for helping.

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