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. DHCP
• D. ICMP

Answer: (A)

Mapping an IP address to a hardware MAC address on a local network is done with ARP. When a host needs to send a packet to another device on the same subnet, it checks its ARP cache for the corresponding MAC. If the mapping isn’t known, it broadcasts a request asking, “Who has this IP address? Tell me your MAC,” and the device with that IP replies with its MAC address. The sender then uses that MAC to construct the Ethernet frame and communicates directly at the data-link layer. This mechanism is specific to IPv4 on local networks; IPv6 uses a different process (Neighbor Discovery). The other protocols serve different roles: DNS translates domain names to IPs, DHCP assigns IP addresses and network configuration, and ICMP handles error messages and network testing rather than address resolution.

Mapping an IP address to a hardware MAC address on a local network is done with ARP. When a host needs to send a packet to another device on the same subnet, it checks its ARP cache for the corresponding MAC. If the mapping isn’t known, it broadcasts a request asking, “Who has this IP address? Tell me your MAC,” and the device with that IP replies with its MAC address. The sender then uses that MAC to construct the Ethernet frame and communicates directly at the data-link layer. This mechanism is specific to IPv4 on local networks; IPv6 uses a different process (Neighbor Discovery). The other protocols serve different roles: DNS translates domain names to IPs, DHCP assigns IP addresses and network configuration, and ICMP handles error messages and network testing rather than address resolution.