|  | 3.1 | Basic LAN Devices
| 3.1.8 | Switches
A switch is a layer 2 device just as a bridge is. In fact a switch is called a multi-port bridge, just like a hub is called a multi-port repeater. The difference between the hub and switch is that switches make decisions based on MAC addresses and hubs don't make decisions at all. Because of the decisions that switches make, they make a LAN much more efficient. They do this by "switching" data only out the port to which the proper host is connected. In contrast, a hub will send the data out all of its ports so that all of the hosts have to see and process (accept or reject) all of the data. Switches at first glance often look like hubs. Both hubs and switches have many connection ports, since part of their function is connectivity concentration (allowing many devices to be connected to one point in the network). The difference between a hub and a switch is what happens inside the device. The purpose of a switch is to concentrate connectivity, while making data transmission more efficient. For now, think of the switch as something that is able to combine the connectivity of a hub with the traffic regulation of a bridge on each port. It switches packets from incoming ports (interfaces) to outgoing ports, while providing each port with full bandwidth (the transmission speed of data on the network backbone). You will learn more about this later. The symbol for a switch is shown in the graphic. The arrows on top represent the separate paths data can take in a switch, unlike the hub, where the data all flows on all paths.
| Web Links
| Cisco Systems