If a host receives a frame addressed to a destination MAC that the host does not recognize, what does the host do?

• A. The host replies to the switch with its own IP address.
• B. The host forwards the frame to all other hosts.
• C. The host will discard the frame.
• D. The host returns the frame to the switch.

Answer: (C)

In Ethernet, a network interface card accepts frames only if the destination MAC matches its own MAC, or if the frame is a broadcast or multicast frame the NIC is interested in. If the destination MAC does not belong to the host and isn’t a broadcast/multicast address, the NIC discards the frame. The switch handles forwarding based on MAC addresses, but the host itself does not forward or reply—so the appropriate action is to discard the frame.