Prerequisite for configuring BFD

C.

BFD (Bidirectional Forwarding Detection) is a protocol used to detect failures in the forwarding path between two routers. When a failure is detected, BFD provides rapid notification to the routers so that they can take appropriate action. In order to configure BFD, there are a few prerequisites that need to be met. Let's look at each answer option in detail to understand which one is correct.

A. Jumbo frame support must be configured on the router that is using BFD. This answer is not correct. Jumbo frame support is not a requirement for configuring BFD. Jumbo frames are packets that are larger than the standard Ethernet frame size of 1500 bytes. While jumbo frames can be useful in some network environments, they are not related to BFD.

B. All routers in the path between two BFD endpoints must have BFD enabled. This answer is correct. In order for BFD to be effective, it must be enabled on all routers in the path between the two BFD endpoints. This includes both intermediate routers and the endpoints themselves. If BFD is not enabled on all routers in the path, it may not be able to detect failures in the forwarding path.

C. Cisco Express Forwarding must be enabled on all participating BFD endpoints. This answer is not correct. Cisco Express Forwarding (CEF) is a forwarding technology used by Cisco routers, but it is not a requirement for configuring BFD. BFD can be used with any forwarding technology that supports IP routing.

D. To use BFD with BGP, the timers 3 9 command must first be configured in the BGP routing process. This answer is partially correct. If you want to use BFD with BGP, you do need to configure the "timers 3 9" command in the BGP routing process. However, this is not a prerequisite for configuring BFD itself. It is only a requirement if you want to use BFD with BGP.

Therefore, the correct answer to this question is B: All routers in the path between two BFD endpoints must have BFD enabled.