On Thu, 2012-04-26 at 11:47 +0200, Ondrej Zajicek wrote:

On Fri, Apr 20, 2012 at 02:32:57PM +0200, Laurent GUERBY wrote:

...

Hi,

I have two debian BIRD routers R1 and R2 connected by an iBGP session, both R1 and R2 are connected to two eBGP peers each:

P1 <==> R1 <===> R2 <===> P3 P2 <==> | | <===> P4

Some routes are imported by R1 from both P1 and P2 and I want to continue to export to P3 a mix of routes from P1 and P2 (which is what is done by the iBGP session and preferences) but now I want to export to P4 only the routes imported from P2 and no route imported from P1.

You could filter out routes from P1 by something like 'export where bgp_next_hop = 1.2.3.4', but less preferred routes from P2 are not even propagated to R2 by R1,

Right that's what I saw.

the simple solution would be to use independent BIRD instance for session to P2 (and iBGP to R1 and R2).

Two instances on R1 would mean that P1 and P2 would need to configure two BGP sessions if I understand correctly your proposal, this isn't an option for us unfortunately. Would having two iBGP sessions between R1 and R2 work using different "source address" and neighbor address ? May be using pipe to control flow of routes, iBGP session B1 receiving routes from P1 and P2 while iBGP session B2 only from P1? Are there BGP options/RFC not implemented by BIRD that would allow transmitting the same route multiple times according to some criteria? Thanks in advance, Laurent