I am currently running my SBG6580 in bridge mode with Cox. I have to agree that it seemed kind of convoluted to get it to function that way, but the instructions below got me there:
How to run a Motorola SBG6580 in Bridge mode:
1. Unplug coax cable from Motorola
2. Hold down the white reset button on the back panel with a pen for 30s. This resets all settings to factory defaults.
3. When modem is back on plug in a computer with an Ethernet cable into the modem (say, Port #1).
4. Your computer should get an IP of 192.168.0.2, and you should be able to connect to »192.168.0.1
and login with admin / motorola
5. Now make the following changes:
* Wireless -> Primary Network -> Disable (this will disable the wireless features of the modem)
* Basic -> DHCP -> Disable
* Basic -> NAPT Mode -> Disable (this is one of the settings that makes the router into a simple bridge).
The router will restart itself now, continue when its back on.
6. Connect port 1 on the Motorola modem to the WAN port of your router. Plug the coaxial cable back into the modem and power cycle it.
7. Once the modem synchs up, your router should have requested and received a public IP address. If this is not the case, click to Renew Lease in the router interface. It may also be necessary to power cycle your router at this point. Also, check to make sure that your router is configured for DHCP in the WAN settings.
(Note: at step 4 if you are unable to access the SBG6580 at 192.168.0.1 then try the alternate address of »192.168.100.1/
(Note: at step 6 it may be necessary to power cycle the modem several times for it configure itself as a simple modem.)
(Note: if you are unable to log into your SBG6580 for any reason during the process, use the back door login name of root with the password of motorola)
As I recall, the steps above went without a hitch, but the SBG6580 did restart more often than indicated in the instructions. At any rate, once the modem got itself squared away, my router received the appropriate external IP address and it has all been good since then.
Politicians are the only people in the world who create problems and then campaign against them. (Charlie Reese)