350-401 Question 14
Single answerAn enterprise network is configured with HSRP to provide high availability for a critical service. During a planned maintenance window, the network administrator upgrades the software on the primary router, causing it to reboot. The secondary router takes over as the active router. After the primary router comes back online, it automatically becomes the active router again. What configuration is MOST LIKELY responsible for this behavior?
- A
Preemption is enabled on the primary router with a higher priority.
- B
The secondary router is configured with a higher HSRP priority than the primary router.
- C
The HSRP group is misconfigured, causing a split-brain scenario.
- D
SSO (Stateful Switch Over) is improperly configured between the routers.
Show answer and explanation
Correct answer: A
Explanation
In HSRP, preemption ensures that the router with the highest priority becomes the active router. By default, HSRP does not allow a higher-priority router to take over the active role once it has been lost unless preemption is explicitly enabled. In this scenario, preemption is enabled on the primary router, which has a higher priority than the secondary router, allowing it to regain the active role automatically after rebooting.
- A. Correct.
Preemption allows a router with a higher priority to take back the active role in an HSRP group after it comes online. This explains why the primary router automatically became active again after rebooting.
- B. Incorrect.
If the secondary router had a higher priority, it would retain the active role even after the primary router came back online unless preemption was configured. This is not the most likely scenario based on the behavior described.
- C. Incorrect.
A split-brain scenario occurs when two devices operate as active routers simultaneously due to misconfiguration or lack of communication. However, there is no indication of this behavior in the scenario.
- D. Incorrect.
SSO is a high availability technology used within a single device (such as a chassis with dual supervisors) and is unrelated to the behavior of HSRP between two separate routers.