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Difficulty: MediumFirst Hop Redundancy Protocols (HSRP and VRRP)

A network engineer is configuring HSRP version 2 on interface GigabitEthernet0/1 of a Cisco IOS router. The interface has been assigned an IPv4 address of 192.168.50.1/24192.168.50.1/24. The engineer enters the command `standby 10 ip 192.168.50.1` under interface configuration mode. Which statement accurately describes the operational result of executing this command?

  1. The router rejects the command with an error because HSRP does not permit the virtual IP address to match an interface physical IP address.Answer
  2. B
    The router accepts the command and automatically sets its HSRP priority to 255 to become the permanent IP address owner for the group.
  3. C
    The command is accepted, and HSRP successfully transitions to the Active state using 192.168.50.1192.168.50.1 as both physical and virtual addresses.
  4. D
    The command is accepted, but HSRP remains in the Listen state until a secondary standby IP address is configured on the interface.

Answer

The router rejects the command with an error because HSRP does not permit the virtual IP address to match an interface physical IP address.
In HSRP (both version 1 and version 2), the virtual IP address must be an unused IP address within the local subnet and cannot match the physical IP address of any interface participating in the HSRP group. Attempting to assign the physical interface IP address as the HSRP virtual IP results in an immediate Cisco IOS CLI error.

Step-by-Step Solution

1
Analyze HSRP virtual IP address configuration requirements.
HSRP (v1 and v2) mandates that the virtual IP address must be a unique IP address within the local IP subnet, distinct from all physical interface IP addresses assigned to participating routers.
Preventing duplicate IP usage and ensuring proper ARP resolution and packet routing logic across participating routers.
2
Compare HSRP behavior with VRRP IP address ownership rules.
Unlike VRRP—which allows the virtual IP address to be identical to a router's physical interface IP address (making that router the IP address owner with priority 255)—HSRP explicitly rejects commands attempting to assign an existing physical interface IP address as the standby virtual IP.
Distinguishing protocol-specific rules between Cisco proprietary HSRP and industry-standard VRRP.
3
Determine the CLI command execution outcome.
When `standby 10 ip 192.168.50.1` is entered on an interface already using 192.168.50.1/24192.168.50.1/24, Cisco IOS returns an error message and rejects the configuration.
The CLI parser enforces the HSRP virtual IP constraint upon command execution.

Key Concept

HSRP Virtual IP Address Assignment vs. VRRP IP Address Ownership
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Topics

First Hop Redundancy Protocols (HSRP and VRRP)

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