Ethernet Switches

An Ethernet switches or network switches are network devices that forward and filter OSI layer 2 datagrams between ports based on the MAC addresses in the packets. A switch is distinct from a hub in that it only forwards the frames to the physical ports involved in the communication rather than all ports connected. It can be thought of as a multi-port bridge. Switch learns to associate physical ports to MAC addresses by examining the source addresses of received frames. If an unknown destination is targeted, the switch broadcasts to all ports but not to the source. Switches normally have numerous ports, facilitating a star topology for devices, and cascading additional switches.

There are new generation switches known as Multi-Layer or Layer-3 switches, which are capable of routing based on layer 3 addressing or additional logical levels.