Many large companies have corporate data networks that are founded on a collection of LANs and routers. From the user's point of view, this arrangement provides them with a physically diverse network that looks like one coherent resource. Routers have the ability to connect different networks together. Routing uses network addresses to decide where to send data. Routers enable public networks to be used between LAns which can reduce costs.
Routers provide, flexibility.
The facilities on most LANs are very powerful. Most organisations do not wish to have small separate computing facilities. They usually want to extend facilities over a wider area so that groups can work without having to be located. Bridges are specialised devices that allow two or more LANs to be connected. The bridge is the more basic device and can only connect LANs of the same type.