bgp router with multi asn's - neighbor config ?

Ondrej Zajicek santiago at
Thu Sep 4 16:32:58 CEST 2014

On Thu, Sep 04, 2014 at 12:32:46PM +0000, Leo Vandewoestijne wrote:
> > > We want to establish a router ('A') announcing two different ASNs
> > > (as1,as2) to it's neighbours. In fact we want to setup three routers A,
> > > B and C, all of them corporately announcing as1 and as2.
> > > 
> > 
> > You cannot have two BGP relations to a single peer. I see two options:
> > 
> You will certainly have to do this on different IP's.
> And actually I only do it with different IP's in different netmasks.

Yes, you can have two BGP sessions between two BGP neighbors if you use
two pairs of IP addresses, IMHO it should work even if all addresses have
the same netmask.

> I think this config is exactly what's requested.
> It was written for use on FreeBSD (using multifib).
> At one point I got collisons, and I did all my best to prevent that (with success).
> So probaly you can make it more simple.

> listen bgp address port 179;
> listen bgp address port 179;

I don't think you should have two 'listen bgp' options. AFAIK there is
only one listening BGP socket in BIRD, but it is OK to have it listen on (default value). Incoming sessions are dispatched based on their
source addresses.

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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