Adding and deleting communities...

Ondrej Zajicek santiago at
Sat May 22 11:55:34 CEST 2010

On Thu, May 20, 2010 at 04:41:04PM +0200, Simone Morandini wrote:
> Hi all,
> I need your help to understand what I'm missing...
> One of the rs clients sends a route with no-export community, so I have  
> to strip it on ingress and re-attach it on egress. I thought I have two  
> alternatives: using "interpret community no" in the bgp table of the  
> peer, or playing with bgp_community.add and delete.

I don't understand why you want to strip and then reattach the no-export
community and not just keep it attached all the time. BIRD internally
interpret this community immediately before export to a BGP *protocol*,
so it is not really important if the community is attached when the
route is in the master table or going through pipes.

If you attach the no-export community in the pipe export filter, then it
is here before the export to the BGP protocol (MYPEER), therefore it
wouldn't be exported unless the protocol has 'interpret communities no'
set. If the BGP protocol has 'interpret  communities no' set, it should
export the route regardless of any communities, solely based on its
export filter. If you have this option set to no (as you wrote)
and still don't see the route on the other side, there is some
problem. You could set 'debug { routes }' for the BGP protocol
to see (in logs) if the route was really exported to the BGP

Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3,
"To err is human -- to blame it on a computer is even more so."
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