Editing Network topology (section)

===Switches===
A [[network switch]] is a device that forwards and filters [[OSI layer 2]] [[datagram]]s ([[Frame (networking)|frames]]) between [[Computer port (hardware)|ports]] based on the destination MAC address in each frame.<ref>{{cite web
|url=http://www.webopedia.com/TERM/s/switch.html
|title=Define switch.
|date=September 1996
|website=Webopedia
|access-date=April 8, 2008
}}</ref>
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.<ref>{{cite web|url=http://compnetworking.about.com/cs/internetworking/g/bldef_bridge.htm|title=What bridge devices and bridging do for computer networks|access-date=2017-10-24|archive-date=2012-04-20|archive-url=https://web.archive.org/web/20120420022720/http://compnetworking.about.com/cs/internetworking/g/bldef_bridge.htm|url-status=dead}}</ref> 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 switch]]es 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).