DNS configured on your local NAS/server is LAN IP address of C9? You can access them locally with their LAN IP: port?

Firmware version is up to date? You can login its web interface and finish the setup, and then, you cannot login the web interface, right? How about status of all lights after step 4? Can you find...

Yes! No worries...

Hi Ermiek, check Internet and DSL section on Status page if the problem continues. I'm not asking for screenshot of DSL Settings page...lol

Configure bandwidth control. Or disable UPnP. Firmware of your W8970 is up to date, right?

Hi Automan, provide the detailed topology(how did you connect all devices). Back up the current settings, save the config file and send it with login username and password to TP-LINK support team for...