A network administrator configures Hot Standby Router Protocol (HSRP) across two core routers to provide default gateway redundancy for a critical server VLAN. During a scheduled maintenance test, the active router is powered down. Logs confirm that the standby router successfully transitions to the active state. However, servers on the VLAN immediately lose external network reachability. Upon reviewing network settings, the administrator discovers a configuration error on the servers. Which of the following is the most likely cause of this connectivity loss?
- The servers were configured with the physical IP address of the primary router as their default gateway instead of the HSRP virtual IP address.Answer
- BThe servers were assigned a static default gateway pointing to the physical IP address of the backup router.
- CThe backup router was configured with an HSRP priority value of 110, forcing Spanning Tree Protocol to place its interface into a blocking state.
- DThe HSRP virtual MAC address was automatically rejected by server network interfaces due to a duplicate IP address conflict notification.
Answer
The servers were configured with the physical IP address of the primary router as their default gateway instead of the HSRP virtual IP address.
For First Hop Redundancy Protocols like HSRP or VRRP to provide seamless gateway failover, all host devices on the subnet must use the shared virtual IP (VIP) address as their default gateway. When the primary router fails, the standby router assumes ownership of the VIP and handles incoming traffic using the shared virtual MAC address. If hosts are incorrectly configured with the physical interface IP of the primary router, their traffic continues to target the powered-down router, resulting in connectivity loss.
Step-by-Step Solution
Key Concept
FHRP Virtual IP Configuration for Host Default Gateways