input filter to set outgoing prefferences

Arjan Filius iafilius at xs4all.nl
Thu Jun 10 14:26:23 CEST 2010


Thanks a lot!

tested bgp_local_pref and works fine!
prepending with the peer AS didn't cross my mind.

Thanks.

Arjan Filius

On Thu, 2010-06-10 at 14:13 +0200, Ondrej Zajicek wrote:

> On Thu, Jun 10, 2010 at 09:57:59AM +0200, Arjan Filius wrote:
> >    Hello bird-users,
> > 
> >    (email send in html to prevent text wrapping, .txt version attached)
> > 
> >    running bird 1.2.3 ppa x64 ubuntu 10.04LTS. 2 bird routers connected with
> >    2 iBGP sessions over different links.
> > 
> >    I'm trying to route specific outgoing traffic over a specific Transit.
> >    It starts with that I'm not really sure how to do it, so tested a bit.
> >    Setting Local performance
> >    on protocol definition works just fine for a complete  Transit, however
> >    when i want to do it more fine grained, i run into trouble.
> 
> You mean local preference (LOCAL_PREF BGP attribute)? You can set local
> preference in filters for specific routes like other attributes (using
> 'bgp_local_pref'). That would probably do what you want.
> 
> >    First started with prepending routes in bgp input filter with my own AS,
> >    which works OK on a single bird router, however, with iBGP all prepended
> >    local AS-es are stripped, and that concept doesn't work.
> 
> You can also prepend peer AS on incoming routes. If you keep such routes
> in your AS it should be OK.
> 
> >    Then, started to set the preference in the bgp input filter, which also
> >    works fine on a single bird router, but that preference seems not to
> >    propagate to the second iBGP router.
> 
> Yes, (protocol) preference is not BGP attribute, but it is internal BIRD
> metric to be able to compare routes from different protocols (BGP/OSPF/static
> ...)
> 
> Protocol preference (route attribute 'preference') and BGP local preference
> (route attribute 'bgp_local_pref') are different concepts.
> 


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