Cisco Certified Internetwork Expert (CCIE) Practice Test

What can cause a failover event on an active/standby setup?

1. The stateful failover link fails

2. The active unit experiences interface failure above the threshold

3. The active unit fails

4. The unit that was previously active recovers

The correct answer is: The active unit fails

In an active/standby setup, the primary condition for triggering a failover event is when the active unit fails. This encompasses instances where the primary device is rendered non-operational, whether due to a hardware malfunction, a critical software crash, or power loss. When the active unit cannot function anymore, the standby unit detects this condition and initiates a failover to take over the responsibility of handling traffic or other functions that the active unit performed. This process ensures high availability and minimal disruption in network services, as the standby unit is typically kept updated with configuration and session state information, allowing it to seamlessly assume operations without significant delays or data loss. Other events, such as link failures or exceeding specified interface failure thresholds, may also contribute to failover scenarios, but they primarily operate under specific configurations or thresholds set in the system rather than the complete failure of the active unit itself.