I would like to configure my linux box to act as its own router, or maybe the better way to put it is that I want the box to connect to the internet directly with no router. There are some other questions that deal with linux-as-a-router, but these deal with situations where the linux box is actually routing to other computers. This does not apply to my situation, where only the single box is the endpoint. One reason I want to do this is that I need to have my cable modem in bridge mode so that Airport Express will work on it. Also, I would just as soon like to configure the routing (or lack of routing actually) using Linux rather than monkey around with the ISP's web interface to their modem.
Since the box is the endpoint, I assume I do not need internal addresses like 192.168.0.1 because there is no LAN, so my box's IP can just be the public facing WAN IP address. In general I think I only need to set up a few services, like DNS. What are the steps to get the box talking to the bridge?
System is Debian Wheezy. Provider is Comcast XFinity and the modem is an Arris TG862G-CT.
Just to re-iterate. I do not actually need to do any routing. There is no LAN. I just need to get the linux box sending packets out over the bridge. Presumably I need to enter static addresses, or possibly MAC addresses somewhere. I have the MAC address of the modem.
As an example of the basic problem operating in bridge mode, the web interface for the modem is probably sitting at 192.168.0.1 but since there is no router, I have no way to access that address without configuring it somehow.