What is a switch?
A switch is a network device with multiple ports in one network whose task is to copy frames from one port to another.
Switches operate at Layer 2 of the OSI Model, the Data-Link Layer. This is in contrast to routers, which operate at Layer 3 of the OSI Model, the Network Layer.
A switch stores the MAC Address of every device which is connected to it.
The switch will then evaluate every frame that passes through it. The switch will examine the destination MAC Address in each frame.
Based upon the destination MAC Address, the switch will then decide which port to copy the frame to.
If the switch does not recognize the MAC Address, it will not know which port to copy the frame to. When that happens, the switch will broadcast the frame to all of its ports.
Switches vs. Hubs
Before switches became available, devices called hubs were common.
Hubs were less intelligent network devices that always copied all frames to all ports.
By only copying frames to the destination ports, switches utilize network bandwidth much more effectively than hubs did.
Switches vs. Bridges
Another piece of network hardware related to the switch is the Bridge. A Bridge is effectively a two-port switch.
Because there is not much market for a two-port switch, bridges are no longer manufactured.
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