Which protocol resolves an IPv4 address to a MAC address on the local network?

• A. ARP
• B. DNS
• C. ICMP
• D. SNMP

Answer: (A)

Local address resolution is handled by ARP. When a device on a LAN needs to send an IPv4 packet to another host on the same network, it must know the destination’s MAC address to place in the Ethernet frame. ARP fills this gap by broadcasting a request asking who has the specific IPv4 address, and the device that owns that IP replies with its MAC address. The requester stores this mapping in an ARP cache for quick reuse, so future packets can be sent without repeating the discovery.

If the destination is outside the local network, ARP is still used, but only to reach the gateway’s MAC address on the local segment—the router then takes over to forward the packet onward. DNS, ICMP, and SNMP don’t resolve MAC addresses: DNS maps domain names to IPs, ICMP handles error messages and diagnostic traffic, and SNMP is for network management.