[ixpmanager] BIRD / Route Server: Load-balancing traffic for member with multiple connections

[Kyle Spencer]

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> 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).
> 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
> 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> 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
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>
>
> --
> André Grüneberg, Managing Director
> andre.grueneberg at bcix.de
> +49 30 2332195 42
>
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> Germany
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