350-401 Question 200
Single answerAn enterprise network is deploying a first-hop redundancy protocol (FHRP) to ensure high availability for its gateway. The network administrator has configured HSRP on two routers, R1 and R2, with the following details:
- R1 is configured with a priority of 110.
- R2 is configured with the default priority.
After the configuration, users report intermittent gateway reachability issues. What could be the most likely cause of the problem?
- A
The HSRP priorities are mismatched, causing the routers to alternate as active and standby roles.
- B
Preemption is not enabled on R1, preventing it from taking over as the active router when it has the higher priority.
- C
The HSRP group number is configured incorrectly, causing both routers to act as active.
- D
The timers for HSRP hello and hold intervals are inconsistent between R1 and R2.
Show answer and explanation
Correct answer: B
Explanation
In HSRP, preemption allows a router with a higher priority to take over as the active router when it becomes available. In this scenario, R1 has a higher priority (110) than R2 (100 by default), but without preemption enabled, R1 cannot take over as the active router, leading to intermittent issues as the network may inconsistently direct traffic. Enabling preemption on R1 would resolve the problem.
- A. Incorrect.
HSRP priority mismatches do not cause routers to alternate roles; rather, the router with the highest priority becomes the active router. This is not the cause of the issue.
- B. Correct.
HSRP preemption must be enabled on the router with the higher priority to allow it to take over as the active router. Without preemption, R2 (with the default priority of 100) remains the active router even though R1 has a higher priority.
- C. Incorrect.
Incorrect group numbers would result in the routers belonging to different HSRP groups, but this would not cause intermittent reachability issues. Instead, users would consistently use the active router of one group.
- D. Incorrect.
Inconsistent HSRP timers could cause reachability issues, but this is less likely to be the cause in this scenario since no timer configuration details were provided.