found at: http://fascinated.fm/post/2379188731/getting-a-motorola-sbg6580-into-bridge-mode-on
Getting a Motorola SBG6580 into “Bridge” mode on TimeWarner Wideband
- Unplug coax cable from Motorola
- Hold down the white reset button on the back panel with a pen for 30s. This resets all settings to factory defaults. The modem will be auto-reconfigured once you plug in the coax cable.
- When modem is back on plug in a computer with an Ethernet cable into the modem.
- Connect to http://192.168.0.1 and login with “admin” / “motorola”
- Now you will make some changes:
- Wireless -> Primary Network -> Disabled
- Basic -> Setup -> NAPT Mode -> Disabled
- Basic -> DHCP -> No
- Advanced -> Options -> Rg Passthrough -> Enable
- Advanced -> Options -> Passthrough Mac Addresses -> Add WAN MAC address of your router 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.
@electroman00
People need to place the modem often in bridged mode when dealing with VOIP applications, gaming (i.e. xbox one complains about strict NAT), configuring a vpn, etc to avoid double NAT scenarios. When in bridge mode the external interface of the device behind the SBG6580 will receive the Comcast Public IP that was once assigned to the external interface on the cable modem. The SBG6580 also had a known issue with it's wireless (I believe with certain firmwares) that it would drop the wireless network intermittently - you could plug in via a wired connection and connectivity would work without issue. The Firewall and other features on the SBG6580 are also lacking to say the least.