300-440 Question 40
Single answerAn enterprise network engineer is configuring Bidirectional Forwarding Detection (BFD) to monitor the forwarding path between two routers running OSPF. The engineer notices that, even when the forwarding path fails, OSPF does not react as quickly as expected. What is the MOST likely reason for this behavior?
- A
The BFD session is not established between the two routers.
- B
The OSPF hello and dead interval timers are overriding the BFD detection timers.
- C
BFD is not supported with OSPF in this specific hardware platform.
- D
The BFD session is operating in asynchronous mode instead of demand mode.
Show answer and explanation
Correct answer: B
Explanation
BFD provides fast failure detection for routing protocols like OSPF by monitoring the forwarding path. However, for BFD to work effectively with OSPF, the OSPF hello and dead interval timers must be configured to leverage BFD's faster detection capabilities. If these timers are not adjusted, OSPF may still rely on its default timers, leading to slower reaction times.
- A. Incorrect.
If the BFD session is not established, BFD would not function at all, and OSPF would rely solely on its own timers. However, the issue here is slow reaction despite BFD being configured.
- B. Correct.
OSPF timers (hello and dead intervals) can override BFD detection timers if they are not configured to work together. This results in slower failure detection by OSPF even when BFD is operational.
- C. Incorrect.
BFD is widely supported across Cisco platforms with OSPF, and hardware compatibility issues are not typically the reason for slow reaction times.
- D. Incorrect.
The mode of BFD operation (asynchronous or demand) does not directly affect the speed of failure detection in this scenario. Both modes allow BFD to detect failures efficiently.