A switch is a network connection device. It typically has four or more ports that can be connected to networked devices (most commonly ethernet devices).
All of the ports in a switch are equal.
The function of a switch is to receive data on any port and then send that data to the port corresponding to its intended destination.
Switches “learn” what ports correspond to specific destinations by examining the data being sent across its connections.
For example, if machine “A”, connected to the switch on port #3, sends data through the switch, then the switch has learned that machine “A” is connected to port #3. Subsequent data that the switch receives destined for machine “A” need only be sent down port #3, and no other port.
Contrast the behavior with that of a hub,which does not learn, but simply sends every packet of data that it receives to all available ports.
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