After must searching I found the user manual to my exact modem. It says its just a DSL router. Anyway, it say that it has embedded administration services: the internal Web (HTTP) Port (TCP 80) and the internal Telnet Server Port (TCP 23).
Is this info useful? I have no clue what Telnet is.
UPDATE 1: The Cayman Gateway can be used as a bridge, rather than a router. As an Internet access device, a
bridge connects the home computer directly to the service provider’s network
equipment with no intervening routing functionality, such as Network
Address Translation. If your service provider’s network is set up to provide your Internet connectivity
via bridge mode, you can set your Cayman Gateway to be compatible.
When configured in Bridge Mode, the Cayman will act as a pass-through
device and allow the workstations on your LAN to have public addresses
directly on the internet.
Configuring for Bridge Mode
1. Browse into the Cayman Gateway’s web interface.
2. Click on the Configure button in the upper Menu bar.
3. Click on the LAN link.
It seems I have to download a program or something....
UPDATE 2: I figured out that the IP of my modem is
http://172.16.0.254 but whenever I go there is sends me directly to it's oen diagnostics page. All papges setup by Earthlink. I feel like I'm hacking something.
UPDATE 3: HAHAH I found a program called HyperTerminal in windows. I setup a new connection and told it to use IP. I put in my modem's ip address and told it to use the TELNET port that I found above (23). The light came on on the modem then I promptly got a message saying unable to connect.

If I put in the IP address and tell it to use the HTTP port (80) it connects! for 3 seconds like disconnects, showing nothing on the screen.
Why would they make Home networking so difficult for their customers...oh wait, $9.95 / month.