[ixpmanager] BIRD / Route Server: Load-balancing traffic for member with multiple connections
Frank Habicht
geier at geier.ne.tz
Sun Jun 21 09:23:06 IST 2026
Hi,
I seem to remember that there once was a presentation at Euro-IX [?] by
VIX (Vienna) about how they try to localise traffic on a single
IXP POP/site.
When, for instance, the destination-peer has two connections at separate
POPs, and traffic from source-peer at location A should not be sent to
destination-peer on location B while destination-peer also has a
connection on location A. But I can't find it now.
[i hope that's the original question...?]
https://www.vix.at/en/technology-services/bgp-communities seems to
reflect current practice.
Regards,
Frank
sorry if OT for IXPManager
On 6/19/2026 9:32 PM, Salvador Bertenbreiter via ixpmanager wrote:
> Hi André,
> Great point, I think MED should solve the issue of which one is the
> preferred gateway.
>
> About Add Path Tx, I will read more about that, it sounds like a great
> solution to offer multi-site balance solution using ECMP.
>
> Best regards
>
>
> Sent from Gmail Mobile
>
> El El vie, 19 jun. 2026 a la(s) 11:06, Kyle Spencer via ixpmanager
> <ixpmanager at inex.ie <mailto:ixpmanager at inex.ie>> escribió:
>
> Thanks for raising this.
>
> We are multi-site and some customers have multi-site redundancy.
> They manage flows by remotely enabling/disabling interfaces at
> either end. This seems like a much better solution.
>
> Might be good to add something about this to the docs :)
>
> On Fri, Jun 19, 2026 at 9:16 AM André Grüneberg via ixpmanager
> <ixpmanager at inex.ie <mailto:ixpmanager at inex.ie>> wrote:
>
> Dear Salvador,
>
> It's part of the features of a route server that it only sends
> one -- the "best path" -- route to it's neighbors.
> I assume the tie breaker in your case will be the router ID (see
> https://bird.nic.cz/doc/bird-2.17.5.html#bgp-route-select-rules
> <https://bird.nic.cz/doc/bird-2.17.5.html#bgp-route-select-rules>).
> If the peer is announcing multiple prefixes, they could set e.g.
> different MEDs for each prefix, so Bird would have some earlier
> tie breaks towards the other router.
>
> Besides all that, you could enable Add Path Tx. This will give
> the peers' routers the chance to employ ECMP (or their own
> policies FWIW).
>
> We have enabled this on our route servers for quite some time
> now. It's just adding a line "add paths tx;" to the channel in
> the BGP protocols in the Bird config.
>
> You may find this in our skinned version of the Bird config:
> https://github.com/bcix/IXP-Manager/blob/
> f5acc6bfdee8479041623479b9606e5c2033f098/resources/skins/bcix/
> api/v4/router/server/bird2/rs01/neighbors.foil.php#L373
> <https://github.com/bcix/IXP-Manager/blob/
> f5acc6bfdee8479041623479b9606e5c2033f098/resources/skins/bcix/
> api/v4/router/server/bird2/rs01/neighbors.foil.php#L373>
> Maybe Barry wants to add this feature to the default distribution?
>
> Unfortunately not all peers' routers have Add Path Rx enabled on
> their side. So, you may want to educate your peers to enable it
> for BGP sessions with route servers.
>
> Hope this helps,
> André
>
> On Fri, 19 Jun 2026 at 04:26, Salvador Bertenbreiter via
> ixpmanager <ixpmanager at inex.ie <mailto:ixpmanager at inex.ie>> wrote:
>
> Hi community,
>
> I hope you are doing well.
>
> We have a case involving a member with two separate
> connections to the peering LAN. Each connection has its own
> IP address, and both sessions are established with our Route
> Server.
>
> The member is concerned because all downstream traffic, from
> their perspective, is currently being received through only
> one of the two connections.
>
> I checked the Looking Glass, and both connections are
> announcing the same prefixes with the same AS-PATH. However,
> BIRD consistently selects all prefixes as primary via only
> one of the two sessions.
>
> The member mentioned that they are not able to announce
> more-specific prefixes from one router and less-specific
> prefixes from the other router, which would otherwise be a
> possible way to influence traffic distribution.
>
> I was wondering if there is any recommended way to achieve
> some form of load-balancing in this scenario. Specifically:
>
> 1. Is it possible for the Route Server / BIRD to "load-
> balance" between two equivalent next-hops for the same
> prefix, so that downstream traffic towards the member
> can be distributed across both connections?
> 2. If ECMP is not supported or not recommended in this
> context, is there a way in IXP Manager or BIRD to
> influence which session is preferred? For example, can
> we assign a higher local preference to one of the
> member’s sessions so that the Route Server selects that
> connection as the primary next-hop?
> 3. More generally, what would be the recommended
> operational approach for handling members with multiple
> connections announcing the same prefixes to the Route
> Server?
>
> Any guidance or best practices would be greatly appreciated.
>
> Best regards,
>
> Salvador Bertenbreiter
>
> _______________________________________________
> INEX IXP Manager mailing list
> ixpmanager at inex.ie <mailto:ixpmanager at inex.ie>
> Unsubscribe or change options here: https://www.inex.ie/
> mailman/listinfo/ixpmanager <https://www.inex.ie/mailman/
> listinfo/ixpmanager>
>
>
>
> --
> André Grüneberg, Managing Director
> andre.grueneberg at bcix.de <mailto:andre.grueneberg at bcix.de>
> +49 30 2332195 42
>
> BCIX Management GmbH
> Albrechtstr. 110
> 12103 Berlin
> Germany
>
> Geschäftsführer/Managing Directors: Jens Lietzmann, André Grüneberg
> Handelsregister: Amtsgericht Charlottenburg, HRB 143581 B
>
> _______________________________________________
> INEX IXP Manager mailing list
> ixpmanager at inex.ie <mailto:ixpmanager at inex.ie>
> Unsubscribe or change options here: https://www.inex.ie/mailman/
> listinfo/ixpmanager <https://www.inex.ie/mailman/listinfo/
> ixpmanager>
>
>
>
> --
> Cell / WhatsApp / Signal: +256786350675
> _______________________________________________
> INEX IXP Manager mailing list
> ixpmanager at inex.ie <mailto:ixpmanager at inex.ie>
> Unsubscribe or change options here: https://www.inex.ie/mailman/
> listinfo/ixpmanager <https://www.inex.ie/mailman/listinfo/ixpmanager>
>
>
> _______________________________________________
> INEX IXP Manager mailing list
> ixpmanager at inex.ie
> Unsubscribe or change options here: https://www.inex.ie/mailman/listinfo/ixpmanager
More information about the ixpmanager
mailing list