ARP
also: Address Resolution Protocol
Address Resolution Protocol (ARP) is a network protocol that maps IP addresses to physical MAC addresses on a local network, allowing devices to find each other's hardware addresses.
ARP operates at Layer 2-3 of the network stack and is essential for communication on local area networks (LANs). When a device needs to send data to another device on the same network segment, it must know the destination's MAC address. ARP broadcasts a request asking "who has this IP address?" and the device with that IP responds with its MAC address.
For example, if your computer (192.168.1.100) wants to contact 192.168.1.50, it sends an ARP broadcast. The device at 192.168.1.50 replies with its MAC address (e.g., aa:bb:cc:dd:ee:ff), and your computer caches this mapping in its ARP table.
You can view your ARP table on Linux using arp -a or ip neigh show. ARP is stateless and vulnerable to spoofing attacks, where malicious hosts claim ownership of IP addresses to redirect traffic.