Which protocol is used to resolve a Layer 2 address of another device?

The correct choice, ARP (Address Resolution Protocol), is specifically designed to map a Layer 2 address (MAC address) to a Layer 3 address (IP address). When a device needs to communicate with another device on the same local network but only knows the IP address of that device, it uses ARP to find out the corresponding MAC address. This process is essential for devices to successfully format Ethernet frames and send them to the correct hardware destination.

ARP operates at the network layer and involves broadcasting a request to all devices on the LAN, asking "Who has this IP address?" The device that recognizes the IP address responds with its MAC address. This dynamic resolution allows devices to function effectively within a network, ensuring that data is sent to the proper recipient.

Other protocols mentioned do not serve this purpose. ICMP (Internet Control Message Protocol) is used primarily for error messages and operational information in IP networks but does not resolve MAC addresses. DNS (Domain Name System) translates domain names to IP addresses, while RARP (Reverse Address Resolution Protocol) maps MAC addresses to IP addresses, which is less commonly used in modern networking. Therefore, among the options provided, ARP is the definitive protocol used for resolving Layer 2 addresses.