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?

August 2, 2023

Q. 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

Ans: X sends an ARP request packet with broadcast MAC address in its local subnet

Solution:

In the Address Resolution Protocol (ARP) process, when a machine (X) wants to find the MAC address of another machine (Y) in the same local subnet, it sends an ARP request packet with a broadcast MAC address (FF:FF:FF:FF:FF:FF) and the IP address of the target machine (Y). The ARP request is broadcasted to all machines on the local subnet. When machine Y receives the ARP request, it will reply to machine X with its MAC address, and the two machines will update their ARP caches with each other’s IP-to-MAC mappings for future communication.