Bidirectional Forwarding Detection Use cases

[tsepo135maroibaki]

I have two routers with dual links between them with some layer 2 technologies in between, i am using IBGP ECMP to load-balance traffic between them, and I have ISIS as an underlying IGP for internal reachability. I would like to enable the BFD to detect failure within the layer 2 network so that the BGP sessions are not affected, do I have to enable it on the ISIS or the IBGP, or both? What are your recommendations for my use case? IBGP session is enabled on the loopbacks.

[MHM Cisco World]

Draw topolgy if you can 

MHM

[tsepo135maroibaki]

CR1 and CR2 are running both ISIS and IBGP.

[MHM Cisco World]

If link between two CR's is L2 then you can use bgp 

If there is Hops between CR's (i.e. one of SW is L3SW) then use bgp multihop

And you need config it under bgp.

MHM

[tsepo135maroibaki]

I am using BGP multihop, there is no L3 hop within the L2 networks. My circuits flaps if there is a failure between the L2 switches which is not detected by ISIS on time or say during high link flaps (within the L2 network).