Which information does a switch use to populate the MAC address table?

Which information does a switch use to populate the MAC address table?

• A. The destination MAC address and the outgoing port
• B. The source MAC address and the incoming port
• C. The source and destination IP addresses
• D. The VLAN ID and the interface number

Answer: (B)

A switch populates its MAC address table by learning which devices are connected to its ports based on the source MAC address found in the Ethernet frames it receives. When a frame arrives at the switch, the switch examines the source MAC address of that frame and associates it with the port that the frame came in on. This enables the switch to build a table that maps incoming MAC addresses to their respective outgoing ports, allowing for efficient frame forwarding. In this context, the source MAC address is crucial because it identifies the device that sent the frame, while the incoming port helps the switch know where to "learn" that address from. This process optimizes network efficiency by ensuring frames are sent only to the intended destination ports, rather than broadcasting to all ports. The other options do not accurately describe the method by which switches learn MAC addresses. For instance, the destination MAC address and outgoing port relate to frame forwarding rather than address learning. Similarly, source and destination IP addresses are relevant in the context of routing and are not utilized by switches for populating their MAC address tables. Lastly, the VLAN ID and interface number may be used in switching processes but do not directly contribute to populating the MAC address table.

A switch populates its MAC address table by learning which devices are connected to its ports based on the source MAC address found in the Ethernet frames it receives. When a frame arrives at the switch, the switch examines the source MAC address of that frame and associates it with the port that the frame came in on. This enables the switch to build a table that maps incoming MAC addresses to their respective outgoing ports, allowing for efficient frame forwarding.

In this context, the source MAC address is crucial because it identifies the device that sent the frame, while the incoming port helps the switch know where to "learn" that address from. This process optimizes network efficiency by ensuring frames are sent only to the intended destination ports, rather than broadcasting to all ports.

The other options do not accurately describe the method by which switches learn MAC addresses. For instance, the destination MAC address and outgoing port relate to frame forwarding rather than address learning. Similarly, source and destination IP addresses are relevant in the context of routing and are not utilized by switches for populating their MAC address tables. Lastly, the VLAN ID and interface number may be used in switching processes but do not directly contribute to populating the MAC address table.