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Zorluk: ZorFirst Hop Redundancy Protocols (HSRP and VRRP)

An engineer is troubleshooting a first-hop redundancy deployment on a Cisco router interface configured with IPv4 address 192.168.100.1/24. When entering the command `standby 1 ip 192.168.100.1`, the CLI outputs `% HSRP: Bad IP address 192.168.100.1`. However, on a neighboring router running VRRP, assigning the physical interface IP address as the virtual IP address is accepted and functions correctly. What fundamental operational difference between HSRP and VRRP causes this behavioral discrepancy?

  1. HSRP mandates that the virtual IP address must be unique and cannot match any physical interface IP in the standby group, whereas VRRP supports IP address ownership where the master router physical IP serves as the virtual IP.Cevap
  2. B
    HSRP requires the preemption feature to be explicitly enabled before assigning a physical IP address as the virtual IP, whereas VRRP enables preemption by default when IP address ownership is configured.
  3. C
    HSRP version 1 only supports virtual IP addresses from private RFC 1918 ranges, whereas VRRP allows both public and private IP addresses to be assigned as virtual router addresses.
  4. D
    HSRP reserves the interface physical IP address exclusively for sending HSRP hello multicast traffic to 224.0.0.2, whereas VRRP uses unicast communication between backup routers.

Cevap

HSRP mandates that the virtual IP address must be unique and cannot match any physical interface IP in the standby group, whereas VRRP supports IP address ownership where the master router physical IP serves as the virtual IP.
In HSRP protocol operations, the virtual IP address MUST be distinct from any physical IPv4 address assigned to the interfaces participating in the HSRP group. Attempting to assign the physical interface IP as the HSRP virtual IP results in a CLI validation error (`% HSRP: Bad IP address`). Conversely, VRRP (RFC 3768 / RFC 5798) explicitly permits IP address ownership, allowing the physical interface IP of the master router to function as the virtual gateway IP address (setting the router priority to 255).

Adım Adım Çözüm

1
Analyze the CLI error output: `% HSRP: Bad IP address 192.168.100.1`.
Identify that the Cisco IOS CLI rejects HSRP configuration when attempting to set the virtual IP equal to the physical interface IP.
Cisco HSRP (both version 1 and version 2) requires the virtual IP to be a separate, unique IPv4 address within the same subnet, distinct from all physical interface IPs assigned to participating routers.
2
Compare HSRP rules with VRRP rules regarding Virtual IP assignment.
Recognize that VRRP allows IP address ownership (where the Virtual IP address matches the physical interface IP address of the Master router).
When a VRRP router owns the IP address, its priority is automatically elevated to 255, making it the VRRP Master.
3
Evaluate the option choices to select the statement accurately explaining this architectural difference.
Select the statement highlighting that HSRP requires a unique virtual IP while VRRP supports IP address ownership.
This correctly identifies why HSRP produced an error while VRRP accepted the physical IP address.

Anahtar Kavram

HSRP vs. VRRP Virtual IP Address Ownership and Assignment Rules
Tahmini Süre:1m 30s
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Konular

First Hop Redundancy Protocols (HSRP and VRRP)

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