300-420 Question 82
Select 3A network engineer is designing a high-availability solution for a multi-site enterprise network. The requirement is to enable fast failure detection and convergence for the OSPF routing protocol across WAN links. Bidirectional Forwarding Detection (BFD) is being considered. Which of the following are true considerations for implementing BFD in this scenario?
- A
BFD requires direct Layer 3 adjacency between the routers for proper functionality.
- B
BFD timers and detection intervals must be tuned carefully to balance failure detection speed and CPU utilization.
- C
BFD is enabled by default on all OSPF neighbors and doesn't require additional configuration.
- D
BFD operates independently of the routing protocol and can detect link failures faster than OSPF's native hello mechanism.
- E
BFD can only be used with OSPF and is not compatible with other routing protocols like BGP or EIGRP.
Show answer and explanation
Correct answers: A, B, D
Explanation
Bidirectional Forwarding Detection (BFD) is a protocol designed for fast failure detection and works independently of routing protocols like OSPF, BGP, and EIGRP. It requires direct Layer 3 adjacency between devices and must be explicitly configured. Proper tuning of BFD timers is essential to ensure rapid failure detection without overloading router CPU resources.
- A. Correct.
Correct: BFD requires a direct Layer 3 adjacency between devices for it to establish a session and detect link failures.
- B. Correct.
Correct: Tuning BFD timers is crucial because overly aggressive settings can cause false positives or high CPU utilization on routers.
- C. Incorrect.
Incorrect: BFD is not enabled by default on OSPF neighbors. It requires explicit configuration to bind BFD sessions to OSPF.
- D. Correct.
Correct: BFD operates independently of routing protocols and provides faster failure detection compared to OSPF's native hello mechanism.
- E. Incorrect.
Incorrect: BFD is not limited to OSPF. It is protocol-agnostic and can work with other routing protocols like BGP and EIGRP.