Cisco CCNA (200-301)IP ConnectivityMedium
R1 and R2 run HSRP for VLAN 10, with R1 configured with priority 120 and standby track on interface Serial0/0/0 with a decrement of 30. R2 is configured with priority 100 and no tracking. If R1's Serial0/0/0 interface fails, what is the result?
- AR1's priority increases to 150, keeping it as the active router
- BR1's priority drops to 30, causing an immediate tie with R2
- CR1's priority drops to 90, and R2 becomes the active router because 100 is now higher
- DR1 remains active because HSRP tracking does not affect priority values
Show answer & explanationAnswer & explanation
Correct answer: C. R1's priority drops to 90, and R2 becomes the active router because 100 is now higher
HSRP interface tracking reduces the priority of the tracked router by the configured decrement when the tracked interface goes down: 120 - 30 = 90. Since 90 is lower than R2's untouched priority of 100, R2 becomes the new active router (assuming preempt is configured, or R2 was never displaced).
Why the other options are wrong
- A. Tracking decrements priority on failure; it never increases it.
- B. The decrement (30) is subtracted from the priority, not used as the new priority value itself.
- D. Interface tracking is specifically designed to lower priority to trigger a role change on link failure.
HSRP Interface Tracking
HSRP tracking monitors the state of a specified interface and decrements the router's HSRP priority by a configured value if that interface goes down, potentially triggering a failover to another router.
- Command: standby 1 track <interface> decrement <value>
- Default decrement value if unspecified is 10
- Lower resulting priority can allow a standby router to become active if preempt is set
Memory trick: Track the link, dock the priority, hand off the throne.