Model : Hardware Version : Firmware Version : ISP : I am replacing my default AT&T router with a new tp-link AC1200. When I plug in my tp-link and connect to the wifi network, I get a "no internet" error message, and the internet light is red on my router. However, when I plug the ethernet cord back into the AT&T router, and connect to its network, everything works fine.I have "Auto-Detect" selected for my DHCP settings. I do not know what other troubleshooting I can do. I do have a stupid sounding question, though: I have an ethernet cable running from a white box on my wall and into the AT&T router. Is that white box essentially my modem? Or, is the AT&T router my modem? Am I unable to get internet because I have to run everything through the AT&T router?Thanks!EDIT: I attached my TP-LINK c1200 ("internet" port) to one of the LAN ports in my AT&T router. I configured router-behind-router settings and now I am connected to my new TP-LINK network. It seems to be working fine.