An organization deploys two edge routers in a First Hop Redundancy Protocol (FHRP) group using HSRP to provide default gateway redundancy for an internal server VLAN. During a scheduled firmware upgrade, the primary active router is rebooted. Network logs confirm that the secondary router successfully transitions from standby to active state and assumes ownership of the virtual MAC address. However, all servers on the LAN immediately lose connection to external networks and fail to route outbound traffic until the primary router finishes rebooting. Which of the following is the most likely cause of this failure?
- The servers were statically configured with the physical interface IP address of the primary router as their default gateway rather than the virtual IP address.Answer
- BThe standby router was configured with a lower bridge priority value, causing Spanning Tree Protocol (STP) to block its uplink switchport upon failover.
- CThe HSRP preemption setting was enabled on the standby router, forcing it to reject virtual router traffic during the active router's offline state.
- DThe default gateway on the servers was set to an unroutable IP address located in a different logical IP subnet.
Answer
The host servers were statically configured using the physical interface IP address of the primary router as their default gateway instead of the HSRP virtual IP address.
For First Hop Redundancy Protocols (such as HSRP or VRRP) to provide seamless gateway failover, all host endpoints must configure the shared Virtual IP (VIP) address as their default gateway. If hosts are incorrectly configured with the physical IP address of a single router, their traffic is directed exclusively to that hardware unit and fails when the device shuts down, regardless of standby router availability.
Step-by-Step Solution
Key Concept
First Hop Redundancy Protocol Virtual IP Configuration