Initially the router modules only determine the remote station to which a data packet is to be sent to. The various parameters for all required connections must be arranged so that a given connection can be selected and established as required. These parameters are stored in a variety of lists, whose interaction permits the correct conections.
A simplified example will clarify this process. Here we assume that the IP address of the computer being searched for is known in the Internet.
- Selecting the correct route A data packet from a computer initially finds the path to the Internet through the IP address of the receiver. The computer sends the packet with this address over the LAN to the router. The router determines the remote station in its IP routing table via which the target IP address can be reached, e.g. 'Provider_A'.
- Connection data for the remote station Using these names, the router checks the remote station list and finds the necessary connection data for the provider. Included in these connection data are, for instance, the WAN interface (DSL, ISDN) through which the provider is connected to, protocol information, or the necessary number for an ISDN call connection. The router also obtains the user name and password required for login from the PPP list.
- Establishing the WAN connection The router can then establish a connection to a provider via a WAN interface. It authenticates itself with a user name and password.
- Transmission of data packets As soon as the connection is established, the router can send the data packet to the Internet.