If your ISP modem came from the ISP themselves, then the modem HW belongs to the ISP and can't be modified in any way as it would break ISP use policy. If you bought a DSL modem from a retail store or online store, then the modem FW is loaded with D-Links OEM FW and not a ISP FW. The differences is that the ISP handles there own FW development for there ISP services that a specific to there Service. D-Links FW is developed for most of not all ISP services in different areas.