If the ISP Modem can be bridged, then you need to use your ISP PPPoE account information input that into the 615 under Setup/Internet/Manual/Conection Type to PPPoE I believe. Your ISP should be able to help you bridge the ISP modem if they support it. Ensure Always ON is selected on the 615 options as well. Power off both Modem and 615, Power ON the modem and let it get ready then power ON the 615. Should have internet if set up right.