Because bridges operate only on Layer 2, they are not adequate for complex networking environments. They have largely been replaced by routers. Whereas bridges connect two LAN segments together into one larger continuous LAN, routers enable individual, unique, logical networks to communicate with each other while maintaining their own unique identity. Routers will also protect networks from unwanted users by restricting access to your data. To use them, your system must use IP or IPX as the transport protocol.
Routers contain addresses to two or more networks at the same time.
Depending on the situation, a router may send packets to a station on the network or to another router. Simple routers transmit packets across separate networks that use the same protocols. Routers come in many styles, sizes and features. Or, they may be software running on a server in conjunction with extra network cards. A feature of routers is that they can choose among several routes to get to the destination.