What is a MAC Table?

A MAC table is used by network switches to map MAC addresses to specific switch ports. This allows the switch to efficiently forward data frames based on their destination MAC address. The switch dynamically builds the MAC table as devices send frames across the network. By maintaining this table, the switch avoids broadcasting data to all ports and sends it directly to the correct destination, improving network efficiency and reduces unnecessary traffic.

Example Scenario: HMI and PLC MAC address is cached in the table:

When the PLC sends a message to the HMI, the switch checks its MAC table to find the HMI’s MAC address. If the switch knows the MAC address of the HMI and the corresponding port, it forwards the data directly to that port.

Example Scenario: HMI and PLC MAC address is not cached in the table:

If the MAC address is not in the table, the switch will broadcast the data to all ports.

Content created by Mike Day