An enterprise router R1 is configured as the active HSRPv1 router for Group 10 with an initial priority of 110 and preemption enabled. R1 tracks its WAN uplink interface GigabitEthernet0/1 with a priority decrement value of 20. Router R2 is configured as the standby router for Group 10 with a priority of 100 and preemption enabled. Place the operational events in the exact chronological sequence following a line-protocol failure on R1's GigabitEthernet0/1 interface until failover convergence completes.
- 1R1 detects a line protocol status change to down on tracked interface GigabitEthernet0/1.
- 2R1 decrements its HSRP priority for Group 10 from 110 to 90.
- 3R1 sends an HSRP Hello packet containing a priority value of 90 to multicast destination 224.0.0.2.
- 4R2 inspects R1's Hello packet and determines its own priority of 100 is higher than R1's priority of 90.
- 5R2 sends an HSRP Coup message to notify R1 that it is preempting the active role.
- 6R2 transitions to the Active state, broadcasts a Gratuitous ARP for the virtual IP address, and R1 transitions to the Standby state.
Cevap
The correct chronological sequence is: (1) R1 detects tracked interface failure -> (2) R1 decrements priority to 90 -> (3) R1 sends Hello with priority 90 -> (4) R2 compares priorities (100 vs 90) -> (5) R2 transmits an HSRP Coup message -> (6) R2 enters Active state and issues a Gratuitous ARP while R1 becomes Standby.
HSRP convergence follows a strict sequence when interface tracking degrades priority: detection of interface failure occurs first, leading to immediate priority calculation on the active router. The reduced priority is then advertised to the standby router via standard Hello messages. The standby router evaluates the lower priority, triggers preemption by sending a Coup message, assumes the Active state, and finally sends a Gratuitous ARP to re-align Layer 2 switch forwarding tables.
Adım Adım Çözüm
Anahtar Kavram
HSRP Interface Tracking and Preemption Mechanism