What protocol is used to find the hardware address of a local device?

Concept

Every device on a local network has two addresses: a logical IP address and a physical hardware (MAC) address. Address resolution is the process of discovering the unknown hardware address that corresponds to a device whose IP address is already known, so that a frame can actually be delivered on the local link.

Applying it here

To send data on a LAN, a host knows the destination IP address but must learn the matching hardware address. The Address Resolution Protocol (ARP) does exactly this: the sender broadcasts an ARP request asking which device owns a given IP address, and the device that owns that IP replies with its hardware (MAC) address, which the sender then caches. This IP-to-hardware mapping on the local network is precisely what the question asks for.

Contrast with the other choices

• RARP works in the opposite direction: a diskless host that already knows its own hardware address uses it to obtain its IP address, so it maps hardware to logical, not logical to hardware.

• IP is a network-layer addressing and routing protocol; it carries packets using logical addresses and performs no hardware-address lookup.

• ICMP is a diagnostic and error-reporting protocol (used by tools like ping); it reports delivery problems and does not resolve addresses.