200-150 Question #173: Real Exam Question with Answer & Explanation

The correct answer is D: by using multicast UDP hello messages. HSRP (Hot Standby Router Protocol) routers in the same group communicate by exchanging Hello messages sent to a well-known multicast address (224.0.0.2 for HSRPv1, 224.0.0.102 for HSRPv2) using UDP. The active router sends these hellos at a configurable hello interval (default 3

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Question

In HSRP, how do interface determine failure and assign standby and active routers?

Options

Aby using Cisco Discovery
Bby using Cisco Spanning Tree protocol
Cby exchanging BPDUs
Dby using multicast UDP hello messages

Explanation

HSRP (Hot Standby Router Protocol) routers in the same group communicate by exchanging Hello messages sent to a well-known multicast address (224.0.0.2 for HSRPv1, 224.0.0.102 for HSRPv2) using UDP. The active router sends these hellos at a configurable hello interval (default 3 seconds). If the standby router does not receive a hello within the hold time (default 10 seconds), it concludes the active router has failed and transitions itself to the active role. CDP (A) is a Cisco discovery protocol used to identify neighboring devices - it plays no role in HSRP failover. Spanning Tree (B) and BPDUs (C) are Layer 2 loop-prevention mechanisms and are completely unrelated to HSRP gateway redundancy.

Topics

#HSRP#first-hop redundancy#hello messages#gateway failover

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