What is the purpose of the MAC address table in a switch?

• A. A router maintains a MAC address table to decide next hop.
• B. A hub maintains a MAC address table to learn devices.
• C. A host maintains a MAC address table to track its own addresses.
• D. A switch maintains a MAC address table that maps MAC addresses to switch ports.

Answer: (D)

The MAC address table on a switch stores mappings of device MAC addresses to the switch port through which that device can be reached. As frames arrive, the switch learns the source MAC and the port it came from, updating the table. This learning lets the switch forward future frames destined for a known MAC out just the correct port, instead of broadcasting to every port. If the destination MAC isn’t yet in the table, the switch floods the frame out all ports in the same collision domain until it learns the destination’s port. Entries age out over time to keep up with changes in the network. This behavior is what lets switches efficiently switch traffic at layer 2; routers use IP routing tables to determine next hops, hubs don’t learn addresses and simply repeat signals, and a host knows its own MAC but does not maintain a network-wide forwarding table.