Connecting LANs, Backbone Networks, and Virtual LANs

* A repeater is a connecting device that operates in the physical layer of the Internet model. A repeater regenerates a signal, connects segments of a LAN, and has no filtering capability.
* A bridge is a connecting device that operates in the physical and data link layers of the Internet model.
* A transparent bridge can forward and filter frames and automatically build its forwarding table.
* A bridge can use the spanning tree algorithm to create a loopless topology.
* A backbone LAN allows several LANs to be connected.
* A backbone is usually a bus or a star.
* A virtual local area network (VLAN) is configured by software, not by physical wiring.
* Membership in a VLAN can be based on port numbers, MAC addresses, IP addresses, IP multicast addresses, or a combination of these features.
* VLANs are cost- and time-efficient, can reduce network traffic, and provide an extra measure of security.