When is a first-hop redundancy protocol needed in the distribution layer?

Question

Options

• Awhen the design implements Layer 2 between the access and distribution blocks
• Bwhen multiple vendor devices need to be supported
• Cwhen preempt tuning of the default gateway is needed
• Dwhen a robust method of backing up the default gateway is needed
• Ewhen the design implements Layer 2 between the access switch and the distribution blocks

• A
  84% (27)
• B
  3% (1)
• D
  9% (3)
• E
  3% (1)

Explanation

A First-Hop Redundancy Protocol (FHRP) such as HSRP, VRRP, or GLBP is required at the distribution layer when Layer 2 (switched) connectivity exists between the access and distribution layers. In this design, access-layer devices use a distribution switch's IP address as their default gateway. If that switch fails, access devices would lose their gateway. An FHRP creates a virtual IP address shared between two distribution switches; if the active one fails, the standby takes over the virtual gateway transparently. In a Layer 3 (routed access) design, routing protocols handle failover automatically and FHRP is not needed. Choice B is incorrect-multi-vendor support is unrelated to FHRP requirements. Choices C and D describe features of FHRP but are not the triggering condition for needing it. Choice E is essentially the same scenario as Choice A but the wording implies a narrower scope; Choice A correctly captures the general design condition.

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