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Difficulty: MediumHigh Availability and Redundancy Concepts

An IT department deploys Virtual Router Redundancy Protocol (VRRP) across two edge routers, Router-1 (Primary, physical IP 10.0.10.2/2410.0.10.2/24) and Router-2 (Backup, physical IP 10.0.10.3/2410.0.10.3/24), to provide default gateway redundancy for a LAN. The virtual router is assigned the Virtual IP (VIP) address 10.0.10.1/2410.0.10.1/24. During a planned failover test, Router-1 is powered down. Although Router-2 correctly assumes the active VRRP Master role, all client workstations on the LAN immediately lose access to external networks. Which of the following host misconfigurations is the most likely cause of this service disruption?

  1. The client workstations were statically configured with the physical IP address of Router-1 as their default gateway instead of the VRRP virtual IP address.Answer
  2. B
    The client workstations were configured to use the VRRP virtual IP address while their subnet mask was set to a point-to-point /30/30 boundary.
  3. C
    The client workstations had Spanning Tree Protocol priority set to the highest numerical value, preventing them from forwarding traffic to the backup gateway.
  4. D
    The client workstations were configured with the VRRP virtual IP address as their primary DNS server rather than as their default gateway.

Answer

The client workstations were statically configured with the physical IP address of Router-1 as their default gateway instead of the VRRP virtual IP address.
For First-Hop Redundancy Protocols (such as VRRP, HSRP, or CARP) to provide seamless gateway failover, all host devices on the local network segment must use the shared Virtual IP (VIP) address (10.0.10.110.0.10.1) as their configured default gateway. If workstations are statically assigned the physical IP address of Router-1 (10.0.10.210.0.10.2), their gateway traffic is sent directly to Router-1's physical MAC address. When Router-1 powers off, Router-2 assumes the VIP, but the workstations continue attempting to send traffic to the offline physical IP address of Router-1, causing a total blackout for external connectivity.

Step-by-Step Solution

1
Analyze First-Hop Redundancy Protocol (FHRP) architecture requirements.
FHRP protocols like VRRP create a shared Virtual IP (VIP) and Virtual MAC address hosted by whichever router is currently acting as the Master.
Host machines must point their default gateway setting to the shared Virtual IP so traffic is transparently routed through whichever physical device holds the Master state.
2
Evaluate the symptom observed during the failover event.
Router-2 successfully became Master, but client traffic stopped flowing to external networks.
If clients were configured with the physical IP of Router-1 (10.0.10.210.0.10.2) as their default gateway, their traffic continues targeting Router-1's physical address directly, failing completely when Router-1 goes offline despite VRRP functioning properly on Router-2.

Key Concept

FHRP Virtual IP Assignment for High Availability
Estimated Time:1m 30s
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Topics

High Availability and Redundancy Concepts

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