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Difficulty: MediumFirst Hop Redundancy Protocols (HSRP and VRRP)

A network administrator is monitoring an HSRP deployment on router R1 and executes the `show standby brief` command, obtaining the following output:

text
Interface Grp Pri P State Active Standby Virtual IP
Gi0/1 20 110 P Active local 192.168.20.3 192.168.20.1

Router R1 is configured to track interface GigabitEthernet0/0 with a priority decrement value of 2020. Router R2 (currently the Standby router at 192.168.20.3192.168.20.3) has an HSRP priority of 100100 and has preemption enabled.

If interface GigabitEthernet0/0 on router R1 goes down, which operational change occurs on the local network segment?

  1. Router R1's priority drops to 9090, causing Router R2 to preempt R1 and assume the Active role for HSRP group 20.Answer
  2. B
    Router R1 remains the Active router because priority tracking decrements only trigger syslog alerts without changing active gateway ownership.
  3. C
    Router R1's priority drops to 9090, but Router R1 remains Active because a Standby router cannot preempt unless its priority exceeds the initial configured priority of 110110.
  4. D
    Router R1 automatically changes its virtual IP address to 192.168.20.3192.168.20.3 to match the IP address of the Standby router.

Answer

Router R1's priority drops to 9090, causing Router R2 to preempt R1 and assume the Active role for HSRP group 20.
When the tracked interface GigabitEthernet0/0 fails on router R1, HSRP interface tracking decrements R1's active priority by 2020, reducing it from 110110 to 9090. Standby router R2 has a priority of 100100 and preemption enabled. Because R2's priority (100100) is now higher than R1's current priority (9090), R2 preempts R1 and transitions to the Active state.

Step-by-Step Solution

1
Calculate Router R1's updated priority following the tracked interface failure.
Initial priority (110110) minus decrement (2020) = 9090.
HSRP interface tracking reduces the local priority by the specified decrement value when the tracked interface enters a down state.
2
Compare Router R1's new priority against Router R2's priority.
Router R1 priority (9090) < Router R2 priority (100100).
Router R2 now has a higher priority than Router R1 on the HSRP segment.
3
Evaluate preemption settings on Router R2 to determine state transition.
Router R2 preempts Router R1, becoming Active, while Router R1 transitions to Standby.
Because Router R2 has preemption enabled, it immediately takes over the Active role once its priority exceeds the current Active router's priority.

Key Concept

HSRP Interface Tracking and Preemption Failover Dynamics
Estimated Time:1m 30s
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Topics

First Hop Redundancy Protocols (HSRP and VRRP)

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