BFD - with multiple routing protocols
The BFD configuration on the interfaces is not linked with any particular routing protocol. By issuing the
bfd command on the interface, you are simply starting the BFD process, and you are setting the parameters (
multiplier etc) with which BFD will communicate with the BFD entity on the other end of the link.
Once the BFD process is up and running, there are no entries created in the adjacency database yet, and no BFD control packets are sent or received yet. The adjacency creation takes place only when you configure BFD support for a particular routing protocol. That’s the
bfd all-interfaces command in the OSPF router mode configuration or the
neighbor fall-over bfd command for BGP.
If you’re running multiple routing protocols on a router, you can enable BFD for multiple routing protocols, and they’ll use the same BFD configuration parameters as they are set out in on the interface configuration.
The BFD interface configuration is a generic configuration (regardless of the routing protocol) that simply enables the BFD process and sets the communication parameters that will be used with the BFD entity on the other end. The routing protocol configuration for BFD enables the operation of BFD for the specific routing protocol, and it will use the parameters set on the interfaces in question to perform the BFD mechanisms.