GATE CSE 2021 Set 1 Q18: Destination MAC addresses of ARP request and reply

Consider the following two statements.

$S_1$ : Destination MAC address of an ARP reply is a broadcast address.

$S_2$ : Destination MAC address of an ARP request is a broadcast address.

Which one of the following choices is correct?

Try it: multiple choice: exactly one correct option

Wrong answer costs 1/3 mark in GATE.

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Answer: C (official GATE 2021 final answer key)

Concept used: ARP requests are broadcast because the target MAC is unknown; the reply is unicast to the requester.

First step: Ask: when the reply is sent, does the responder already know the requester's MAC address?

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Source: official GATE 2021 Set 1 CS question paper and final answer key, organised by IIT Bombay. Question paper · Answer key