What does an ARP request look like?

• A. What is my MAC address?
• B. Who has IP? Tell sender
• C. Reply with MAC address
• D. Where is IP address for host?

Answer: (B)

ARP requests are messages used to learn the MAC address that corresponds to a given IPv4 address. They are sent as a broadcast to all devices on the local network, asking: who has this IP? Tell the sender’s MAC address. The option that matches this exactly is the one that states “Who has IP? Tell sender.” The ARP reply, which is sent only by the device that owns the IP, would be something like “IP X is at MAC Y,” not the request itself. The other phrasings don’t reflect the purpose of ARP, which is to resolve an IP to a MAC on the local network.