Which protocol is used to map an IP address to a MAC address by broadcasting to the local network?

• A. DHCP
• B. DNS
• C. ARP
• D. IPv6 Neighbor Discovery

Answer: (C)

Resolving a local IP to a hardware MAC address is done by a protocol that operates at the link layer to translate network addresses into data-link addresses. Address Resolution Protocol does this in IPv4. When a host needs to send a frame to an IP it doesn’t know the MAC for, it sends an ARP request that is broadcast to all devices on the local network asking, “Who has this IP? Please reply with your MAC.” The device with that IP responds with its MAC address, and the requester caches this mapping for future use so subsequent frames can be delivered directly to the correct hardware address. This mechanism is inherently local to the broadcast domain; it isn’t used beyond the local network.

DHCP is about obtaining IP configuration parameters, not mapping addresses to MACs. DNS translates domain names to IP addresses, not link-layer addresses. IPv6 uses Neighbor Discovery to perform similar functions, but it relies on ICMPv6 rather than ARP.