What is the primary function of the Address Resolution Protocol (ARP)?

The primary function of the Address Resolution Protocol (ARP) is to resolve IP addresses to MAC addresses. When a device on a local area network (LAN) wants to communicate with another device, it needs to encapsulate its data within a frame that includes the MAC address of the destination. However, devices typically work with IP addresses when initiating communications.

When a device knows an IP address but not the corresponding MAC address, it sends out an ARP request to the network, asking which device has that IP address. The device with that IP address responds with an ARP reply, providing its MAC address. This process allows the originating device to learn the MAC address it needs to properly route the packets to the intended recipient on the local network.

Understanding ARP is crucial for network communication, as it facilitates the linkage between layer 3 (Network Layer) addresses, such as IP addresses, and layer 2 (Data Link Layer) addresses, which are MAC addresses.