Local area networks (LANs) can be confusing, especially when LANs have to be linked. Among the questions most frequently asked of us is the difference between bridges and routers. Bridges connect similar types of LANs, for example one Ethernet LAN with another or one TokenRing LAN with another. Bridges are supported by standards which fit into the bottom two levels of the Open System Interconnection (OSI) Reference Model. They are limited to physical and data link connectivity because they are connecting LANs using the same topology. Routers connect different types of LANs, therefore, they have to resolve incompatibilities among them through use of network protocols. Routers work at the third layer of the OSI Reference Model, the network layer. A third type of internetworking technology, the brouter, is emerging which combines the functions of bridges and routers and offers somewhat greater flexibility as the initial investment need not become obsolete as the networks in the environment change. Nevertheless, one of the first questions librarians will need to be able to answer when purchasing products for linking LANs is whether bridges or routers should be quoted.