If a host receives a frame with a destination MAC address it does not recognize, what will it do?

• A. The host will discard the frame.
• B. The host forwards the frame to the switch to update the MAC address table.
• C. The host forwards the frame to the router.
• D. The host forwards the frame to all other hosts.

Answer: (A)

On Ethernet, a host only processes frames whose destination MAC matches its own, or frames addressed to broadcast or multicast groups. If the destination MAC address is not the host’s MAC and it isn’t a broadcast or multicast address, the NIC simply discards the frame. The host doesn’t forward such frames to a switch or router; forwarding decisions are made by network devices like switches, which learn where to send frames by observing source MAC addresses. Since the frame isn’t addressed to this host, it will drop it.