What action does a switch perform when it encounters a source MAC address that is not in its MAC address table?

What action does a switch perform when it encounters a source MAC address that is not in its MAC address table?

• A. The switch drops the frame
• B. The switch adds the MAC address and incoming port number to the table
• C. The switch forwards the frame to all ports
• D. The switch sends a broadcast to all devices

Answer: (B)

When a switch encounters a source MAC address that is not in its MAC address table, it takes the action of adding the MAC address along with the incoming port number to the table. This process is crucial for the switch to efficiently forward frames in the future. The MAC address table, also known as the content addressable memory (CAM) table, is used by the switch to keep track of which devices are connected to which ports. When it sees a source MAC address for the first time, the switch learns that this address is located on the specific port from which the frame was received. By storing this information, the switch can later use it to make intelligent forwarding decisions, sending frames only to the relevant port instead of broadcasting them to all connected devices. This helps optimize network performance by reducing unnecessary traffic. In contrast to this correct action, dropping the frame would mean the switch does not learn anything about the new MAC address, which would be inefficient. Forwarding the frame to all ports or sending a broadcast to all devices would also reduce efficiency and increase unnecessary traffic on the network. Thus, adding the MAC address and port to the table is the appropriate response that supports the switch's role in maintaining an efficient and organized network.

When a switch encounters a source MAC address that is not in its MAC address table, it takes the action of adding the MAC address along with the incoming port number to the table. This process is crucial for the switch to efficiently forward frames in the future.

The MAC address table, also known as the content addressable memory (CAM) table, is used by the switch to keep track of which devices are connected to which ports. When it sees a source MAC address for the first time, the switch learns that this address is located on the specific port from which the frame was received. By storing this information, the switch can later use it to make intelligent forwarding decisions, sending frames only to the relevant port instead of broadcasting them to all connected devices. This helps optimize network performance by reducing unnecessary traffic.

In contrast to this correct action, dropping the frame would mean the switch does not learn anything about the new MAC address, which would be inefficient. Forwarding the frame to all ports or sending a broadcast to all devices would also reduce efficiency and increase unnecessary traffic on the network. Thus, adding the MAC address and port to the table is the appropriate response that supports the switch's role in maintaining an efficient and organized network.