Which protocol is used to map IP addresses to MAC addresses in a LAN?

• A. Address Resolution Protocol (ARP)
• B. Advanced Encryption Standard (AES)
• C. Adware
• D. Anti-Passback System

Answer: (A)

Address Resolution Protocol maps IPv4 addresses to physical MAC addresses on a local area network. When a device wants to send a frame to another device on the same LAN, it first checks its ARP cache for the target IP. If the MAC isn’t known, it broadcasts an ARP request asking who has that IP. The device with that IP replies with its MAC address, and the requester can then encapsulate the IP packet in a frame addressed to that MAC. The mapping is stored in the ARP table for quick use next time. This mechanism is essential because routing relies on IP addresses, while delivering frames on the local link uses MAC addresses. For IPv6, a different mechanism called Neighbor Discovery Protocol handles this mapping. The other options aren’t involved in resolving IPs to MACs: one is an encryption standard, another is unwanted software, and the last is a non-networking access-control system.