A network administrator configures a pair of core routers using a First Hop Redundancy Protocol (FHRP) to provide seamless default gateway redundancy for a corporate subnet. During a scheduled maintenance test, the primary router is powered off. Although the secondary router successfully transitions to the active state and assumes ownership of the virtual IP and virtual MAC addresses, workstations on the subnet immediately lose outbound network access. Upon auditing host network configurations, the administrator notices that all affected workstations were statically configured. Which of the following is the most likely cause of the connectivity failure during failover?
- The workstations were configured with the physical IP address of the primary router as their default gateway instead of the FHRP virtual IP address.Answer
- BThe workstations were assigned a subnet mask that prevents them from resolving the secondary router's physical MAC address.
- CThe secondary router was assigned the highest numerical Spanning Tree Protocol (STP) priority value on its uplink interfaces.
- DThe primary and secondary router interfaces were assigned to separate VLAN broadcast domains on the core switch.
Answer
The workstations were configured with the physical IP address of the primary router as their default gateway instead of the FHRP virtual IP address.
First Hop Redundancy Protocols rely on clients directing traffic to a shared Virtual IP (VIP) address. When host devices are incorrectly configured with the primary router's unique physical interface IP address as their default gateway, their traffic bypasses the FHRP virtual abstraction. Consequently, when the primary device fails, client traffic continues sending packets to the dead physical IP, causing complete outbound loss despite the standby router taking over the active virtual role.
Step-by-Step Solution
Key Concept
FHRP Virtual IP vs Physical Interface IP Gateway Configuration