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Difficulty: MediumFirst Hop Redundancy Protocols (HSRP and VRRP)

A network administrator is migrating a VLAN gateway infrastructure from VRRP to HSRP version 2 on Cisco IOS routers. Under the previous VRRP setup, Router R1 had its physical interface IP address configured as 192.168.10.1/24192.168.10.1/24 and served as the VRRP IP address owner by using 192.168.10.1192.168.10.1 as the virtual IP address.

During the migration, the administrator enters the following commands on Router R1's GigabitEthernet0/0 interface:
text
RouterR1(config)# interface gigabitethernet 0/0
RouterR1(config-if)# ip address 192.168.10.1 255.255.255.0
RouterR1(config-if)# standby version 2
RouterR1(config-if)# standby 10 ip 192.168.10.1

What is the outcome of executing the `standby 10 ip 192.168.10.1` command on Router R1?

  1. Cisco IOS rejects using the interface physical IP address as the HSRP virtual IP address, resulting in a configuration error.Answer
  2. B
    Router R1 accepts the command and automatically becomes the Active router with an unalterable priority of 255255.
  3. C
    The router accepts the command and automatically enables HSRP preemption to ensure primary forwarding status.
  4. D
    The command is accepted only if HSRP version 1 is configured instead of HSRP version 2.

Answer

Cisco IOS rejects using the interface physical IP address as the HSRP virtual IP address, resulting in a configuration error.
Unlike VRRP, which allows a router interface to be the IP address owner by assigning its physical IP address as the virtual IP address (which sets its priority automatically to 255255), Cisco HSRP (both v1 and v2) requires the virtual IP address to be an unused IP address on the IP subnet. Attempting to assign the local interface's physical IP address as the HSRP virtual IP address will be rejected by Cisco IOS.

Step-by-Step Solution

1
Analyze VRRP versus HSRP virtual IP address assignment rules.
VRRP allows a router to act as the IP address owner where the virtual IP address is identical to the router's physical interface IP address (assigning priority 255255). In contrast, Cisco HSRP (both v1 and v2) strictly requires the virtual IP address to be a unique IP address on the subnet that is not assigned to any physical router interface.
Understanding protocol design differences prevents invalid configurations during network migrations.
2
Evaluate the CLI command result on Router R1.
Entering `standby 10 ip 192.168.10.1` while GigabitEthernet0/0 has the physical IP address 192.168.10.1192.168.10.1 causes Cisco IOS to generate an error indicating the virtual IP address cannot match the local physical IP address.
HSRP relies on distinct virtual and physical IP addressing to maintain dual operational capability for ARP and ICMP handling.

Key Concept

HSRP Virtual IP Address Uniqueness Constraint vs. VRRP IP Address Ownership
Estimated Time:1m 15s
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Topics

First Hop Redundancy Protocols (HSRP and VRRP)

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