Switch

Switch is used to connect multiple Computers in a Local Area Network same as the Hub does. Then why we need Switch instead of Hub?

            Switch is an intelligent device whereas Hub got no intelligence. Switch is a Layer 2 device which works at Data Link layer of OSI Model. Layer 2 can recognize MAC Address.

           Switch maintains its own MAC Address table which remembers the Computers MAC.

         Sys A sends data to Sys D, when Switch receives the signal from Sys A it saves the MAC Address of Sys A and it has no idea about Sys D MAC so it simply forwards the signal as Broadcast via all other ports.

          Now Sys D sending reply to Sys A, when Switch receives the signal it saves the MAC of Sys D in the table and now it knows Sys A is located at Port 1 so forwards the signal only via Port 1.

           

Likewise Switch remembers all the MAC Address of the Computers. This method saves Bandwidth and prevents from the collision.