Which action occurs when a switch receives a frame addressed to a multicast MAC address?

• A. The switch forwards it out all ports except the ingress port.
• B. The switch forwards it only to the port associated with the destination MAC.
• C. The switch drops the frame.
• D. The switch floods the frame to the router.

Answer: (A)

Multicast frames don’t have a single destination port. A switch uses its MAC address table for unicast destinations, but for multicast there isn’t one specific port to forward to. To ensure every potential listener in the local VLAN can receive the frame, the switch floods it out of all ports except the ingress port. If IGMP snooping is in use and there are listeners on certain ports, the switch can narrow the forwarding to those ports, but the default behavior is still to flood to all ports in the VLAN. So the best action is to send the frame to all ports except the one it arrived on.