Which protocol maps IP addresses to MAC addresses on a local network?

Which protocol maps IP addresses to MAC addresses on a local network?

• A. Arp
• B. Dns
• C. Tcp
• D. Udp

Answer: (A)

ARP is the protocol that maps IP addresses to MAC addresses on a local network. When a host wants to send an IPv4 frame to another device on the same LAN, it needs the destination’s MAC address. If it doesn’t know it, it broadcasts an ARP request asking who owns that IP, and the device with that IP replies with its MAC address. The sender caches this mapping for future communications, so subsequent frames can be delivered directly at the data-link layer. This resolution happens only within the local broadcast domain. DNS, in contrast, translates domain names to IP addresses, not to MAC addresses, and operates at a higher level across networks. TCP and UDP are transport-layer protocols that carry data between hosts using IP addresses; they rely on IP already being known and do not resolve MAC addresses themselves. For IPv6, the equivalent mechanism is Neighbor Discovery Protocol, not ARP.

ARP is the protocol that maps IP addresses to MAC addresses on a local network. When a host wants to send an IPv4 frame to another device on the same LAN, it needs the destination’s MAC address. If it doesn’t know it, it broadcasts an ARP request asking who owns that IP, and the device with that IP replies with its MAC address. The sender caches this mapping for future communications, so subsequent frames can be delivered directly at the data-link layer. This resolution happens only within the local broadcast domain.

DNS, in contrast, translates domain names to IP addresses, not to MAC addresses, and operates at a higher level across networks. TCP and UDP are transport-layer protocols that carry data between hosts using IP addresses; they rely on IP already being known and do not resolve MAC addresses themselves. For IPv6, the equivalent mechanism is Neighbor Discovery Protocol, not ARP.