Switch is one of many networking hardware that is usually used, but as a customer we rarely see it. It is system administrator’s job to maintain this thing works well as infrastructure support. When we see wireless access point, or see LAN cables, and if we try to follow where the cable ends, we usually will meet this thing. A Box with some RJ-45 slots available, and some indicator lamps on.

Switch, generally works in layer 2, or Data Link Layer, has main function to connect some computers and enable each computer to communicate each other by sending frames. Our internet day today, works with protocol called TCP/IP, rely on this thing to build safer networks. Unlike hub, switch sends each packet to specific destination, so that other destination can not know/see/hear this frame. Using configured switch we can also build virtual lan, or simply lan based on ports. These two things are some major advantages of switch over hub.

To do this “send to specific destination”, swich has built in table that stored “port name” and “specific address” for each port. for example
1 port 1 : freds computer
2 port 2 : brian computer

We can explain how swicth work in this way :

1. first time swicth received frame, it first records the sender address and stored its address and the port in it. then swicth will forward this frame by flooding all ports except the port where the frame came.
2. swicth will wait for the respond from computer with the destination address. when it responds the frame. switch will records the responding computer address and the port where the respond comes.
3. when there is another packet from and to known address and port (has been stored).
it will use the table to send the frame to its special direction
4. if the address hasnt been stored it will do step 1.