Protection from link flap in OSPF/BFD

[Baptiste Jonglez]

Hi,

We are running an OSPF/BFD setup with Bird, with several links that look
like this:

  Bird/Debian -- switch -- fiber -- switch -- Bird/Debian

We had a situation where a fiber link was flapping hard between two
switches because of a hardware issue.  In turn, the BFD sessions were
flapping, which is expected.

My question: is there any way to limit the amount of flapping in either
OSPF or BFD?  I was specifically looking for a "prefer older" option in
OSPF but it only exists in BGP.  Alternatively, BFD could disable a
session for some time if it flaps too much.

In our setup, routers often have several paths with the same OSPF cost
to/from the BGP gateway.  We don't use ECMP: only one path is used at a
time, other paths are used as backup (in case of fiber cut or hardware
issue).

So, in our case, a "prefer older" option for OSPF would make a lot of
sense and would naturally avoid using flapping links.

Is it something that could be implemented?

Thanks,
Baptiste

PS: we are using Bird 1.6.3 which is quite old
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