In IPv4 networks, ARP maps IP addresses to MAC addresses.

• A. ARP maps IP addresses to MAC addresses.
• B. ARP encrypts the payload of IP packets.
• C. ARP resolves domain names to IPs.
• D. ARP provides routing metrics for BGP.

Answer: (A)

ARP translates IPv4 addresses into MAC addresses on the local network so a host can deliver a frame to the correct device. When a device has an IP packet destined for another host on the same LAN, it first checks its ARP cache for the corresponding MAC address. If not found, it broadcasts an ARP request asking, “Who has this IP address? Tell the requester’s MAC.” The owner replies with its MAC address, the mapping is cached, and the frame is then sent to that MAC address. This mapping remains for a limited time and may be updated if the device changes its hardware address.

This is why the statement about ARP is the best answer: it expresses ARP’s fundamental role in linking IP addresses to hardware addresses so data can be properly delivered at the data link layer. The other functions listed—encrypting payload, resolving domain names, or providing routing metrics for BGP—are handled by different protocols (encryption like IPsec/TLS, DNS, and routing protocols, respectively) and do not describe ARP’s purpose.