Which statement about ARP is true?

• A. ARP operates by sending unicast requests to all devices on the local network
• B. ARP uses DNS to map IPs to MACs
• C. ARP routes IP packets between networks
• D. ARP operates by broadcasting requests to learn MAC addresses for known IPs on the local network

Answer: (D)

ARP translates IP addresses to physical MAC addresses on the local network. When a host needs to send a packet to another host on the same LAN and doesn’t know the recipient’s MAC address, it broadcasts an ARP request asking who has that IP address. Every device on the local network hears the request, but only the device with the matching IP replies with its MAC address. The requester then caches this mapping for future use. This behavior—broadcasting to learn MAC addresses for known IPs on the local network—is what ARP does. It isn’t about DNS, which maps names to IPs, and it doesn’t route packets between networks; routing is done by routers. ARP is specific to IPv4, while IPv6 uses Neighbor Discovery for similar functionality.