An enterprise network deployment utilizes two Layer 3 switches, Switch-A and Switch-B, con… — CompTIA Network+

An enterprise network deployment utilizes two Layer 3 switches, Switch-A and Switch-B, configured with VRRP to provide default gateway redundancy for VLAN 20 ( $10.20.0.0/24$ ). Switch-A is configured with physical interface IP $10.20.0.2/24$ and a VRRP priority of 110. Switch-B is configured with physical interface IP $10.20.0.3/24$ and a VRRP priority of 100. The configured VRRP Virtual IP (VIP) is $10.20.0.1/24$ . During an operational audit, it is discovered that half of the host workstations on VLAN 20 were manually configured with a static default gateway of $10.20.0.2$ , while the other half use the VIP $10.20.0.1$ . If Switch-A suddenly suffers a complete power loss, which of the following best describes the resulting traffic routing behavior for hosts on VLAN 20?

Hosts configured with the gateway address $10.20.0.1$ will maintain external connectivity as Switch-B transitions to the VRRP Master role, whereas hosts configured with gateway address $10.20.0.2$ will lose all external connectivity.Answer
B
All hosts on VLAN 20 will lose external connectivity because Switch-B cannot assume the Virtual IP without an active graceful failover handshake from Switch-A.
C
Hosts configured with gateway address $10.20.0.2$ will automatically send ARP requests to resolve Switch-B's physical MAC address and resume external communication.
D
Spanning Tree Protocol (STP) will block all client switch ports on VLAN 20 to prevent a routing loop caused by Switch-B taking over the root bridge priority.

Answer

Hosts using the virtual IP address 10.20.0.1 will maintain continuous connectivity because the backup router automatically assumes the Master state for the VIP. Hosts statically configured with the physical IP 10.20.0.2 of the failed active router will lose external reachability.

In First Hop Redundancy Protocols (FHRP) such as VRRP, high availability is achieved by assigning host devices the shared Virtual IP (VIP) address as their default gateway. When the active Master router (Switch-A) fails, the Backup router (Switch-B) detects the missing advertisement frames and seamlessly assumes ownership of the VIP (

10.20.0.1

). Consequently, all hosts pointing to

10.20.0.1

experience minimal disruption. However, hosts misconfigured to use Switch-A's physical interface IP (

10.20.0.2

) experience total loss of external connectivity because Switch-B never adopts Switch-A's physical IP address.

Step-by-Step Solution

Analyze VRRP Master/Backup state transitions upon hardware failure.

Switch-A (Priority 110, Master) fails and stops sending VRRP advertisements. Switch-B (Priority 100, Backup) misses advertisements beyond the Master_Down_Interval and transitions to Master state, taking ownership of the Virtual IP 10.20.0.1 and Virtual MAC address.

VRRP provides automated gateway failover by shifting the VIP ownership to the surviving node.

Evaluate host connectivity for clients using the Virtual IP 10.20.0.1.

Traffic sent to 10.20.0.1 is routed through Switch-B without requiring any host-side changes.

Hosts send packets to the virtual gateway address, which is now actively serviced by Switch-B.

Evaluate host connectivity for clients misconfigured with Switch-A's physical IP 10.20.0.2.

Traffic directed to 10.20.0.2 receives no ARP responses or Layer 3 processing, causing complete gateway unreachability.

Switch-B only assumes the VIP (10.20.0.1) during failover and does not take over Switch-A's unique physical IP address (10.20.0.2).

Key Concept

FHRP Virtual IP vs Physical Interface Addressing

Estimated Time:3m 0s

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