300-420 Question 83
Single answerAn enterprise network is using Bidirectional Forwarding Detection (BFD) to provide rapid failure detection for OSPF adjacency across a WAN link. During a routine network assessment, the network engineer notices that BFD is not detecting link failures as quickly as expected. Upon further investigation, it is found that the configured BFD timers on the WAN link are too high. What should the network engineer do to ensure faster link failure detection using BFD?
- A
Decrease the BFD minimum interval and multiplier values on both ends of the link.
- B
Enable BFD echo mode to allow higher failure detection sensitivity.
- C
Increase the BFD multiplier value to account for network latency.
- D
Disable BFD on the WAN link and rely on OSPF's dead interval for failure detection.
Show answer and explanation
Correct answer: A
Explanation
To achieve faster failure detection with BFD, it is necessary to adjust the BFD timers. Specifically, decreasing the BFD minimum interval and multiplier values reduces the detection time for link failures. BFD operates by sending control packets at regular intervals, and these settings directly influence how quickly a failure is detected if packets are not received. Other options, such as enabling echo mode or increasing the multiplier, do not directly reduce the detection time.
- A. Correct.
Decreasing the BFD minimum interval and multiplier values reduces the time it takes for BFD to detect a failure, ensuring faster failure detection.
- B. Incorrect.
While enabling BFD echo mode can provide additional validation of the forwarding path, it does not directly influence the BFD timer configuration, which is critical for faster detection.
- C. Incorrect.
Increasing the BFD multiplier value increases the tolerance for missed packets, which delays failure detection rather than speeding it up.
- D. Incorrect.
Disabling BFD and relying on OSPF's dead interval will result in significantly slower failure detection compared to BFD.