What types of mapping does ARP enable?

ARP, or Address Resolution Protocol, is specifically designed to enable the mapping of IP addresses to MAC addresses. In a typical networking environment, devices communicate using IP addresses at the network layer, while the underlying data link layer relies on MAC addresses to facilitate frame delivery. When a device wants to communicate with another device over the local network, it needs to know the MAC address that corresponds to the target device's IP address. This is where ARP comes in; it allows a device to broadcast a request to the local network asking, "Who has this IP address?" The device that owns the IP address responds with its MAC address, enabling the requesting device to send data packets correctly.

In contrast, the other options listed pertain to different types of address mappings that are not related to the function of ARP. IP addresses to port numbers involve transport layer communication, and MAC addresses to hostnames would typically be resolved through a name resolution service like DNS rather than ARP. Subnet masks do not map to IP addresses; instead, they define the network and host portions of an IP address for routing purposes. Thus, the primary function of ARP remains the essential mapping of IP addresses to their corresponding MAC addresses within a local area network.