A circuit in an ADSL is defined by endpoints. A route is defined as the path that is taken between these endpoints. Switching is the process of making a path available for use by a circuit. A router shifts data from one route to another. It also allows for access to various fixed or temporary routes. This they do by recognizing the specific destination address and then copying data from one route to another.

Routers are useful when there are multiple networks. Routes may be permanent or temporary. There are several functions of the router. Routers must essentially contain the address information that is associated with each individual packet. This information can be in the form of full origination and destination information for each packet, or a special identification set up for a particular origination or destination on a temporary basis.

Routers will contain the address tables or a routing directory. This routing directory enables routers to identify and define the path for travel of the data. In a scenario where User A and User B are located on the same LAN, the router does not do anything except examine the packet. If User A and User B are located on different LANs and the router has a node (a direct connection) between the two LANs, then the router also has very little work to do. In this case, the LAN grabs a copy of the packet from the first LAN and puts it on the second LAN.

ADSL routers are particularly useful when they need to access WANs. Consider a scenario to understand the process better. If the User A wants to communicate with User B, where User A is on LAN 1 and User B is not on a LAN, then in this case the router on LAN 1 will make a connection through a WAN to User B, and provide a temporary access route.