Please help me on this. Here is the scenario:
My questions are:
Please advise before we present this to the CAB and implementation. Thank you.
My questions are:
Answer: the implication would be eliminating sub-second millisecond convergence.
BFD detect failure at the link layer very fast , once detected it informs the upper layer protocol about the failure causing it to converge immediately.
Answer: if your Provider experiencing intermittent flaps, then yes it will be advisable to turn BFD off. this however doesn't totally ignore the link flaps, once the upper protocol detect the failure based on the dead interval parameter on OSPF, it will recalculate OSPF routes again. Keep in mind, if you have redundant or more links to your provider , then I wouldn't recommend disabling BFD , as it should improve Convergence and you shouldn't notice the failure.
Answer: disabling BFD allows the router recognize a full down status once the upper protocol dead interval occurs or full down status of interface. which ever occurs the earliest.
You can disable it one by one. or if you have configuration management software, it allows you to do it for all nodes at a time. but this depends if you have it or not.
Please consider not to disable BFD if you have multiple OSPF links towards your provider from any branch, as it shouldn't impact your VMs, it should rather improve Convergence at milliseconds which is absolutely not noticeable.
1.What is the implication in disabling all BFD in routers' interface and sub interface? - Once disabled a BFD session to its peers should be seen in a admin down state, meaning bfd is awaiting to negotiate via a control packet - So its as if BFD isnt applied at the other end.
2.Will this improve recalculation of OSPF routes in cause of link flaps or it will totally ignore the link flaps? - It could - as my understanding is ospf will determine if it needs to terminate its peering session based on bfd, Once bfd is disabled ospf convergence will be as per hello+ dead timers unless you've applied other fast convergence methods and if your link flaps are still occurring and then you could possibly have another issue with you connections.
3.Will the routers only recognize a "full down" status of the interface? - Not sure what your asking here - do you mean if BFD is disabled will opsf take that as a full down status if so - My understanding is No , otherwise answer 2 would be applicable
4.How can we Disable BFD in multiple Router Sub interfaces that participates in OSPF in a faster way? Or do we have to do this one by one? - Not sure there is any other way but manually one by one on subinterface unless the the global bfd all interface disabled command is applicable to bfd configured subinterfaces?