What is the primary function of a MAC address table on a switch?

What is the primary function of a MAC address table on a switch?

• A. Maps MAC addresses to switch ports to forward frames.
• B. Maps IP addresses to MAC addresses.
• C. Stores ARP entries.
• D. Encodes VLAN tags.

Answer: (A)

The main idea here is how a switch uses a MAC address table to move traffic at layer 2. A switch keeps a dynamic map that links each device’s MAC address to the specific port on which that device can be reached. As frames arrive, the switch notes the source MAC and the port they came from, updating or creating those entries. When a frame needs to be forwarded, the switch looks up the destination MAC in the table: if it has a known port, it sends the frame only to that port; if not, it floods the frame to all ports in the same VLAN to discover the destination. Entries age out over time, so the table stays current as devices move. This is not about mapping IP addresses to MAC addresses—that’s done by ARP, which resolves network-layer addresses to data-link addresses. It also isn’t about storing ARP entries or about encoding VLAN tags; those serve different roles—ARP pertains to IP-to-MAC resolution, and VLAN tagging relates to identifying VLAN membership in frames rather than the switch’s MAC-to-port mappings.

The main idea here is how a switch uses a MAC address table to move traffic at layer 2. A switch keeps a dynamic map that links each device’s MAC address to the specific port on which that device can be reached. As frames arrive, the switch notes the source MAC and the port they came from, updating or creating those entries. When a frame needs to be forwarded, the switch looks up the destination MAC in the table: if it has a known port, it sends the frame only to that port; if not, it floods the frame to all ports in the same VLAN to discover the destination. Entries age out over time, so the table stays current as devices move.

This is not about mapping IP addresses to MAC addresses—that’s done by ARP, which resolves network-layer addresses to data-link addresses. It also isn’t about storing ARP entries or about encoding VLAN tags; those serve different roles—ARP pertains to IP-to-MAC resolution, and VLAN tagging relates to identifying VLAN membership in frames rather than the switch’s MAC-to-port mappings.