Switches
A network
switch is a device that
forwards and filters 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. It 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 the
source. Switches normally have numerous ports, facilitating a star topology for
devices, and cascading additional switches.
Multi-layer switches are capable of routing based on layer
3 addressing or additional logical levels. The term switch is often used loosely to include
devices such as routers and bridges, as well as devices that may distribute
traffic based on load or based on application content (e.g., a Web URL identifier).
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