A network engineer configures two Layer 3 switches, Switch-1 and Switch-2, with Virtual Ro… — CompTIA Network+

A network engineer configures two Layer 3 switches, Switch-1 and Switch-2, with Virtual Router Redundancy Protocol (VRRP) to provide default gateway redundancy for a server VLAN ( $172.16.20.0/24$ ). Switch-1 is configured with a VRRP priority of 110 and a physical SVI address of $172.16.20.2$ . Switch-2 has a priority of 100 and a physical SVI address of $172.16.20.3$ . The VRRP Virtual IP (VIP) is assigned as $172.16.20.1$ . After a network maintenance reboot, end-user servers lose connectivity to external subnets whenever Switch-1 undergoes maintenance, despite Switch-2 being fully operational. Troubleshooting reveals that all servers were manually statically configured with $172.16.20.2$ as their default gateway. Which of the following best explains why gateway redundancy failed and identifies the correct solution?

The servers were configured with the physical IP address of Switch-1 rather than the VRRP Virtual IP address; updating host default gateway configurations to $172.16.20.1$ will resolve the issue.Answer
B
Switch-2 requires a higher numerical STP bridge priority value than Switch-1 to allow VRRP state transitions; lowering Switch-1's priority below Switch-2 will resolve the issue.
C
The VRRP Virtual IP address must match the physical interface address of Switch-2 to permit master takeover; reassigning the VIP to $172.16.20.3$ will restore gateway redundancy.
D
VRRP preemption was automatically disabled on Switch-1 during reboot; re-enabling preemption on Switch-1 will force Switch-2 to process traffic when Switch-1 goes offline.

Answer

The host servers were misconfigured to point directly to Switch-1's physical IP address (

172.16.20.2

) instead of the VRRP Virtual IP address (

172.16.20.1

). Configuring all hosts to use the VRRP VIP as their default gateway allows Switch-2 to transparently assume handling gateway traffic via the shared Virtual MAC address if Switch-1 fails.

First Hop Redundancy Protocols (FHRP) such as VRRP rely on workstations and servers using a shared Virtual IP (VIP) address as their default gateway. When hosts are incorrectly configured with the physical IP address of a specific router interface, traffic is routed directly to that single device without leveraging the virtual gateway mechanism. If that specific router fails or goes offline for maintenance, host packets sent to its physical IP are dropped, breaking redundancy. Setting host default gateways to the VRRP VIP ensures traffic floats to the active Master router.

Step-by-Step Solution

Analyze host IP configuration and First Hop Redundancy Protocol (FHRP) architecture.

Identify that host default gateways are set to

172.16.20.2

, which is the physical SVI IP of Switch-1, rather than the VRRP VIP of

172.16.20.1

FHRP protocols like VRRP provide redundancy by generating a shared Virtual IP (VIP) and Virtual MAC address that float between active/backup nodes.

Determine the impact of pointing default gateways to physical interface IPs.

When Switch-1 goes offline, traffic destined to its physical IP (

172.16.20.2

) drops because Switch-2 only responds to ARP requests for the Virtual IP (

172.16.20.1

) when assuming the Master role.

Host packets targeted at a dead physical MAC/IP cannot be intercepted by VRRP Backup routers without host configuration using the VIP.

Select the correct remediation.

Reconfigure server default gateway settings to target the VRRP VIP (

172.16.20.1

This restores high availability, allowing Switch-2 to seamlessly take over default gateway duties upon Switch-1 failure.

Key Concept

FHRP Virtual Gateway IP Configuration

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