The Motorola SBG6580 is a cable modem with a built-in wireless router. If you prefer to use a separate router, you can shut down the wireless antenna and put the SBG6580 into bridge mode by disabling the network address and port translation setting. Disabling NAPT prevents the SBG6580 from handing out IP addresses to connected devices. Like most routers, the SBG6580 has an HTML setup screen where you can change the settings through a computer's browser.
Unplug the coaxial cable from the back of the modem.
Connect a computer to one of the Ethernet ports.
Open the Web browser; then type "http://192.168.0.1" in the address bar. Press "Enter," and the browser will display a login screen.
Enter the user name and password. The default user name is "admin," and the default password is "motorola."
Select the "Basic" tab, and set "NAPT mode" to "Disabled." Click "Apply."
Set the "DHCP" drop-down menu to "No."
Click the "Wireless" tab, and select "Primary Network" on the left menu bar. Set the "Primary Network" drop-down menu to "Disabled."
Click the "Advanced" tab, and select "Options."
Check the "Enable" box next to "Rg PassThrough." Enter the MAC address of your router in the box next to the "Add Mac Address" button; then click the button.
Click "Apply," and restart the modem.
If you have changed the user name or password and don't remember what they are, you can reset the modem to the default settings by pressing the Reset button on the back for approximately 30 seconds.