What happens when a switch receives a frame whose destination MAC address is not in its CAM table?

What happens when a switch receives a frame whose destination MAC address is not in its CAM table?

• A. Drops the frame
• B. Sends to the default gateway
• C. Floods only the VLAN where origin resides
• D. Floods the frame out all interfaces (except the originating interface)

Answer: (D)

When a switch sees a frame and its destination MAC isn’t in the CAM table, it doesn’t know which port to forward it to. The only reliable move is to send that frame out all ports in the same VLAN except the port it arrived on. This floods the frame so the destination device (if present) will see it and respond, allowing the switch to learn the correct port for that MAC address for future frames. So the behavior is to flood to all interfaces in the VLAN except the originating one, which is why the best choice is the option describing that broad flood. This isn’t about dropping the frame or sending it to a specific gateway; it’s a temporary step to discover where the destination lives and to populate the CAM table for future efficiency.

When a switch sees a frame and its destination MAC isn’t in the CAM table, it doesn’t know which port to forward it to. The only reliable move is to send that frame out all ports in the same VLAN except the port it arrived on. This floods the frame so the destination device (if present) will see it and respond, allowing the switch to learn the correct port for that MAC address for future frames.

So the behavior is to flood to all interfaces in the VLAN except the originating one, which is why the best choice is the option describing that broad flood. This isn’t about dropping the frame or sending it to a specific gateway; it’s a temporary step to discover where the destination lives and to populate the CAM table for future efficiency.