Firewall Fundamentals

Most Linksys routers have an extremely small requirements list. Because the assumption is that the router will be connected to a small or home network that lacks any kind of DHCP server, the routers ship with the internal interface configured with the IP address of 192.168.1.1 and are configured to act as a DHCP server to provide IP addresses to any host on the internal network. Therefore, connecting internal hosts to the router for the purpose of configuring the router is very much plug and play. Just plug a host into the internal network of the router (either through the integrated switch on models that feature it, or through a separate hub or switch for models that do not contain a built-in switch), turn the router on, and then turn the computer on. The computer should obtain an IP address, allowing it to communicate with the router.

To provide for the external connectivity, you need to coordinate with the service provider to determine what the requirements are to connect to their network. If the service provider supports DHCP clients, the router will automatically obtain the proper IP address information. If your service provider requires the use of PPPoE or something similar, they will provide you with the appropriate information, and you just configure the router accordingly.

At this point, the router will allow all internal hosts unrestricted access, while allowing no external hosts to initiate access to internal resources.