BIRD BGP and VRF - Cannot assign requested address

[Ondrej Zajicek]

On Fri, Aug 04, 2017 at 04:43:01PM +0200, Clément Guivy wrote:
> Hello, I am trying to set up 2 BIRD routers as AS border routers (on Debian 9).
> ...
> I plan to use both ipv4 and ipv6 and also, on BIRD routers both the forwarding
> and the BGP peerings are to take place in a linux vrf named "internet" (using
> l3mdev, not namespaces or custom ip rules). At the BIRD level I also set up
> a table named "internet".
> ...
> So overall it seems like BIRD fails to bind to one interface, this is possibly
> linked to the kernel VRF setup but I can't see why it doesn't work when the peering
> to downstream routers using the same VRF do work properly.

Hi

I guess that the difference is that EBGP sessions are bound to the
associated interface (direct mode), while IBGP sessions are multihop
and not associated with particular interface (multihop mode).

Although a source address is specified, that is used just for the regular
bind() operation, which AFAIK does not cause TCP connection to be
associated with particular VRF/l3mdev. For that it is necessary to use
SO_BINDTODEVICE socket option, which is used just in the direct mode.

You could try to use 'direct' option for IBGP to run it in IBGP mode.

-- 
Elen sila lumenn' omentielvo

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