I upgraded my Cox cable service in Fairfax from basic (DOCSIS 1.0) and wanted a DOCSIS 3 modem. This Netgear CG3000D was available used locally at an attractive price. The seller assured me it would work on Cox Cable and to some extent it did. I called Cox technical support, gave them the MAC address and Customer Serial Number and I was up in minutes.
I have 5 static IP addresses and to make them work I need to assign the Gateway IP. After a day of searching on and off for the place to set that address in the management screens I gave up and downloaded and read the manual. There are supposed to be two "radio" buttons - "Static" and "Dynamic". They aren't there. That implies the firmware does not match the documentation.
I called Cox and the tech tried to help but insisted I find the radio buttons. I called Netgear and they said it was an ISP supplied unit that came with no support from Netgear. Further investigation leads to GPL (General Public License) meaning open source code was used in developing the firmware. Worried I may be too far down this rabbit hole to get out, I baled and bought a new Motorola cable modem and connected my old Mikrotik router. At least I can reload the firmware on that device.