Bidirectional Forwarding Detection (BFD)

BFD (Bidirectional Forwarding Detection) is a super fast protocol that is able to detect link failures within milliseconds or even microseconds.. All relevant protocols, both routing and otherwise, have some sort of mechanism to detect link failures. For example, OSPF uses hello packets and a dead interval, EIGRP uses hello packets and a holddown timer.

BFD runs independently from any other routing protocols. Once it’s up and running, you can configure protocols like OSPF, EIGRP, BGP, HSRP, MPLS LDP etc. to use BFD for link failure detection instead of their own mechanisms. When the link fails, BFD will inform the protocol.

BFD consists of configurations on interfaces as well as within the routing protocolon interfaces as well as within the routing protocol. It can also be configured on particular static routes under the address-family configuration mode found under a particular VRF. Specific BFD timers can be configured for each individual static route.

In all cases however, BFD configuration is generally linked with the interface. Therefore, while you can create multiple static routes to the same next-hop IP, each with their own metrics, you would not typically configure different BFD intervals for each of those routes if they are using the same outgoing interface.