2 routers and 4 peers route export selection

[Laurent GUERBY]

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