What is the difference between unicast, multicast, and broadcast frames at the data link layer?

• A. Unicast frames deliver to a single MAC address; multicast frames deliver to a group; broadcast frames deliver to all devices on the LAN.
• B. Unicast frames deliver to all devices, multicast frames to a single device, broadcast frames to a group.
• C. Unicast frames delay delivery, multicast frames prioritize traffic, broadcast frames duplicate frames.
• D. Unicast frames are only for IPv6, multicast/broadcast only for IPv4.

Answer: (A)

At the data link layer, delivery is determined by the destination MAC address. A unicast frame is targeted to a single device, so only that host will process the payload—the switch forwards it to the port belonging to that MAC. A multicast frame uses a group MAC address, so devices that have joined the group will process it, with the switch delivering the frame to all ports that have group members. A broadcast frame uses the special broadcast MAC address and is delivered to all devices on the local network segment; every NIC on that LAN segment receives it, though higher-layer protocols decide what to do with it. This describes the three delivery scopes accurately: single device, a group, or all devices on the LAN. The other statements mix up who receives the frames, or wrongly tie the concepts to IPv4 vs IPv6 (IPv6 relies on multicast rather than a distinct data-link broadcast).