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Mac address learning process
Mac address learning process





In the initial stage, the switch does not know any MAC addresses at all. A basic example is described below of how a switch, connected to three servers, builds its MAC address table and forwards or floods frames. The same will happen if the switch receives a frame with a broadcast/multicast destination address with the difference that this time the destination of the frames is the well-known broadcast/multicast address. This process is called unknown unicast flooding. What happens though when the switch receives a frame with a destination MAC address that is not included in the table? In that case the switch will just broadcast/flood the frame with the unknown destination address to all of its ports (apart from the port where the frame came from). That means that next time the switch receives a frame with this MAC address as a destination, it will know –by looking in its address table- to which port to forward that frame. Every time a switch receives a new frame, it stores the source MAC address of that frame along with the port from where it received it in its table.

mac address learning process

But how does a switch actually think and take forwarding decisions?Ī switch learns MAC addresses from the frames it receives and then stores this information in an internal table. A switch is a layer 2 device, which means that it processes frames and forwards them based on MAC addresses.







Mac address learning process