Suppose that in an IP-over-Ethernet network, a machine X wishes to find the MAC address of another machine Y in its subnet. Which one of the following techniques can be used for this? A) X sends an ARP request packet to the local gateway's IP address which then finds the MAC address of Y and sends to X B) X sends an ARP request packet to the local gateway's MAC address which then finds the MAC address of Y and sends to X C) X sends an ARP request packet with broadcast MAC address in its local subnet D) X sends an ARP request packet with broadcast IP address in its local subnet

Official answer: C) X sends an ARP request packet with broadcast MAC address in its local subnet. Explanation: In an IP-over-Ethernet local network, the Address Resolution Protocol (ARP) is used to map an IP address to a physical (MAC) address [cite: 3, 5]: 1. When machine X wants to find the MAC address of machine Y located on the same subnet, it creates an ARP Request packet containing Y's IP address [cite: 5]. 2. At the Data Link layer, this ARP request is encapsulated into an Ethernet frame with the destination MAC address set to the broadcast MAC address (`FF:FF:FF:FF:FF:FF`) so that all machines in the local subnet receive and process the frame [cite: 5]. 3. Machine Y recognizes its own IP address in the ARP request and responds with a unicast ARP reply containing its MAC address [cite: 5]. Therefore, machine X sends an ARP request packet with the broadcast MAC address in its local subnet [cite: 5]. Hence, option (C) is correct.

A) X sends an ARP request packet to the local gateway's IP address which then finds the MAC address of Y and sends to X

B) X sends an ARP request packet to the local gateway's MAC address which then finds the MAC address of Y and sends to X

D) X sends an ARP request packet with broadcast IP address in its local subnet

Data Link Layer

GATE CSE 2019 · Q29

MCQ2 marksEasy

Time00:00

Suppose that in an IP-over-Ethernet network, a machine X wishes to find the MAC address of another machine Y in its subnet. Which one of the following techniques can be used for this?

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Solution

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Official answer: C) X sends an ARP request packet with broadcast MAC address in its local subnet

Data Link Layer

In an IP-over-Ethernet local network, the Address Resolution Protocol (ARP) is used to map an IP address to a physical (MAC) address [cite: 3, 5]:

When machine X wants to find the MAC address of machine Y located on the same subnet, it creates an ARP Request packet containing Y's IP address [cite: 5].
At the Data Link layer, this ARP request is encapsulated into an Ethernet frame with the destination MAC address set to the broadcast MAC address (FF:FF:FF:FF:FF:FF) so that all machines in the local subnet receive and process the frame [cite: 5].
Machine Y recognizes its own IP address in the ARP request and responds with a unicast ARP reply containing its MAC address [cite: 5].

Therefore, machine X sends an ARP request packet with the broadcast MAC address in its local subnet [cite: 5].

Hence, option (C) is correct.

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This Data Link Layer previous year question is Q29 of the GATE CSE 2019 paper. Find more GATE CSE PYQs on Data Link Layer in Computer Networks, or browse all GATE CSE PYQs.

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Data Link Layer in GATE CSE

Data Link Layer has 27 GATE CSE PYQs across 17 papers from 2013 to 2026. 10 of them are 2-mark MCQs like this one, and it is the only one in GATE CSE 2019.

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