If the destination MAC address is found on the MAC address table, the switch forwards the Ethernet frame via the corresponding port of the MAC address.

The destination MAC address is important to determine the port number which the destination device is connected. When a Layer 2 Ethernet frame reaches a port on the Network Switch the switch reads the source MAC address of the Ethernet frame as a part of learning function, and it also reads the destination MAC address also as a part of forwarding function. Forwardingįorwarding is the process of passing network traffic a device connected to one port of a Network Switch to another device connected to another port on the switch. Aging helps to remove old entries and free memory of MAC address table to add new entries. Timers are used in aging process of old entries. Whenever switch updates an entry in the MAC address table, the switch resets the timer for that entry. This will normally happen when network administrators remove the cable from one port and attach it to another port. If the port numbers are different, the switch updates the MAC address table new port number. If the MAC address is already available in the MAC address table, the switch compares the incoming port with the port already available in the MAC table. If the switch cannot find a corresponding entry in MAC address table, the switch will add the address to the table with the port number via the Ethernet frame arrived. When a frame reaches into the port of a switch, the switch reads the MAC address of the source device from Ethernet frame and compares it to its MAC address table (also known as CAM (Content Addressable Memory) table). Learning is the process of obtaining the MAC address of connected devices.

Three basic functins of a switch are Learning, Forwarding and Preventing Layer 2 Loops.

Multi switch mac address learning