Babel/OSPF with multiple routers claiming the same route

[Maiyun Zhang]

Hi All,

I’m trying to implement a topology where multiple nodes have connections to one network. Let’s say there are three devices running babel:
A 10.0.0.1/24
B 10.0.0.2
C 10.0.0.3
and both B and C can route traffic to 10.1.0.0/16, and BIRD learns this route through the `kernel` protocol.

Now that both B and C announces 10.1.0.0/16 via babel, and it seems that BIRD does some kind of “first come first serve”, and A only sees the route via one of B or C.
Let’s say B comes online first and announces the route. Now C comes online. It doesn’t announce 10.1.0.0/16 to babel at all. The same behaviour is observed if I use ospf instead of babel.

My hypothesis is that when it synchronizes kernel with master4, it sees that 10.1.0.0/16 is already in master4 (announced by B), and so it doesn’t import this route from kernel to master4 at all(?)

What I am trying to do is to have both B and C announce this route, and let babel choose whether traffic from A for 10.1.0.0/16 should go to B or C based on its metric. Is this possible? or is it a really bad idea?

Thanks.

Best,

Maiyun Zhang (he/him)

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://trubka.network.cz/pipermail/bird-users/attachments/20250317/2e298285/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 4315 bytes
Desc: not available
URL: <http://trubka.network.cz/pipermail/bird-users/attachments/20250317/2e298285/attachment.p7s>