An engineer configured OSPF on all routers in the data center in the same exchange as other routers. Layer 2 connectivity was established. Now, the engineer plans to implement BFD to detect failures i

Question

Options

• AConfigure IS-IS routing before implementing BFD.
• BConfigure BFD between each adjacent router.
• CConfigure BFD on any one of the routers.
• DConfigure CEF before implementing BFD.

• A
  15% (5)
• B
  76% (25)
• C
  6% (2)
• D
  3% (1)

Explanation

BFD (Bidirectional Forwarding Detection) is a peer-to-peer protocol - a session only forms when both routers in an adjacency have BFD configured. Because the data center has multiple routers, the engineer must configure BFD on each router pair (i.e., every adjacent link), not just on one side or one device.

Why the distractors are wrong:

• A (IS-IS required): BFD is routing-protocol-agnostic. It integrates with OSPF, BGP, IS-IS, and others - no protocol swap is needed.
• C (one router only): A BFD session cannot form unilaterally. Both ends must participate; configuring only one router leaves all sessions incomplete.
• D (CEF required): While CEF is a prerequisite for BFD on some Cisco platforms, it is enabled by default on modern IOS routers. The OSPF network described is already functional, making this a non-issue and a distractor rather than the required action.

Memory tip: The "B" in BFD stands for Bidirectional - remember that both sides of every link must be configured. Think of it like a phone call: one person picking up isn't enough; the other end has to answer too.

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