Which protocol maps IP addresses to MAC addresses on a local network?

Which protocol maps IP addresses to MAC addresses on a local network?

• A. TCP
• B. UDP
• C. ICMP
• D. ARP

Answer: (D)

Understanding how a host finds the hardware address corresponding to an IP on the same network is essential for delivering packets. The protocol that handles this mapping is ARP. When a device wants to send to an IP on the local segment and doesn’t know the MAC, it broadcasts an ARP request asking who owns that IP. The owner replies with its MAC, and both devices update their ARP caches. With the MAC known, the data link layer can deliver the frame to the correct hardware address. ARP is designed for IPv4 on local networks and sits between the IP layer and the Ethernet (or other) data link layer. The other protocols don’t perform this mapping. TCP and UDP operate at the transport layer to deliver data between processes, assuming the MAC address is already known. ICMP handles diagnostic and error messages for IP packets, not address resolution.

Understanding how a host finds the hardware address corresponding to an IP on the same network is essential for delivering packets. The protocol that handles this mapping is ARP. When a device wants to send to an IP on the local segment and doesn’t know the MAC, it broadcasts an ARP request asking who owns that IP. The owner replies with its MAC, and both devices update their ARP caches. With the MAC known, the data link layer can deliver the frame to the correct hardware address. ARP is designed for IPv4 on local networks and sits between the IP layer and the Ethernet (or other) data link layer.

The other protocols don’t perform this mapping. TCP and UDP operate at the transport layer to deliver data between processes, assuming the MAC address is already known. ICMP handles diagnostic and error messages for IP packets, not address resolution.