Initially, the router modules only determine which remote site a data packet should be sent to. In order for the required connection to be selected and/or established, various parameters need to be agreed for all of the necessary connections. These parameters are stored in different lists, which interact to allow the correct connections.
A simplified example will illustrate this process. Here we assume that you know the Internet IP address of the computer you are looking for.
- Selecting the right routeA data packet from a computer initially finds its way to the Internet by means of the IP address of the recipient. The computer sends the packet with this address through the LAN to the router. The router refers to its IP routing table to determine which remote site is used to reach the IP address in question, e.g. 'Provider'.
- Connection data for the remote siteThe router uses this name to check the list of remote sites and find the connection data required for the provider. This connection data includes, for example, the WAN interface (DSL, ISDN) used to reach the provider, protocol information, or the number required for an ISDN dial-in connection. The router also refers to the PPP list to obtain the corresponding user name and password.
- Establishing the WAN connectionThe router then establishes a connection to the provider via a WAN interface. It authenticates itself by user name and password.
- Transmission of data packetsOnce the connection is established, the router sends the data packet to the Internet.
