An enterprise network utilizes two Layer 3 switches, Switch-A and Switch-B, to provide def… — CompTIA Network+

An enterprise network utilizes two Layer 3 switches, Switch-A and Switch-B, to provide default gateway redundancy for VLAN 30 ( $172.16.30.0/24$ ). Switch-A is configured as the HSRP Active router with a priority of 120 and preemption enabled, using Virtual IP (VIP) $172.16.30.1$ (physical IP $172.16.30.2$ ). Switch-B is the HSRP Standby router with a default priority of 100 and physical IP $172.16.30.3$ . Switch-A is also configured as the STP Root Bridge for VLAN 30. During a routine host setup, a technician manually sets a critical server's default gateway address to $172.16.30.2$ instead of the HSRP VIP. Later, Switch-A's tracked WAN uplink fails, decreasing its HSRP priority by 30 points and causing Switch-B to assume the HSRP Active role. Which of the following best describes the immediate pathing behavior for outbound traffic originating from this server?

Outbound packets from the server continue targeting Switch-A's physical MAC address, forcing Switch-A to route the traffic across the inter-switch trunk link to Switch-B for external forwarding.Cevap
B
Outbound packets from the server fail completely because losing the HSRP Active state causes Switch-A to immediately shut down its physical Layer 3 interface and ARP processing.
C
The server automatically detects the HSRP failover event via Gratuitous ARP and dynamically updates its gateway ARP entry to target Switch-B's physical MAC address.
D
Outbound packets are blocked by Spanning Tree Protocol (STP) because the HSRP priority decrement automatically triggers an STP topology change that transitions Switch-A's access ports to a blocking state.

Cevap

Outbound packets from the server continue targeting Switch-A's physical MAC address, forcing Switch-A to route the traffic across the inter-switch trunk link to Switch-B for external forwarding.

When host workstations are incorrectly configured to use the physical IP address of a redundant router instead of the FHRP Virtual IP (VIP), they resolve ARP directly to the physical interface's MAC address. If an HSRP failover occurs, the physical interface of the former active router remains online and continues to receive and route packets sent directly to it. However, because external outbound paths may now prefer or traverse the newly active router, traffic from misconfigured hosts must cross the inter-switch trunk, leading to suboptimal hairpin routing and negating true gateway redundancy for that host.

Adım Adım Çözüm

Analyze host gateway address resolution

The host server uses IP

172.16.30.2

(Switch-A physical IP) as its default gateway rather than VIP

172.16.30.1

Host traffic targeting a physical IP is encapsulated with the specific destination MAC address of that physical interface.

Evaluate FHRP state changes and interface operational status

Switch-A's priority drops from 120 to 90 (

120 - 30

), causing Switch-B (priority 100) to become Active for HSRP. However, Switch-A's physical LAN interface remains up and functional.

FHRP standby transition only changes ownership of the Virtual IP/MAC; physical interfaces remain active unless physically down.

Trace packet flow from misconfigured host

Packets arrive at Switch-A, which routes them toward their external destination via Switch-B over the inter-switch trunk link.

Switch-A retains Layer 3 routing functionality and forwards packets matching its routing table, even when acting as HSRP Standby.

Anahtar Kavram

First Hop Redundancy Protocol (FHRP) Virtual IP Configuration vs Physical Interface Forwarding

Soru

Cevap

Adım Adım Çözüm

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