People are trying to help. No one can help you if you already have your mind made up what the problem is. You seem to believe you can just switch routers by unplugging the old one and plugging in the new one and all will work fine. It usually won't.
Have you tried setting it up your router / modem in bridge mode? I had to set mine up in bridge mode before everything functioned well.
What is the IP address of your cable modem? Is it the same as the IP on your RT-AC66U?
Are you trying to use the same IP address on the RT-AC66U as you had on your Linksys (default 192.168.1.1)?
Try changing the IP of the RT-AC66U to something else like 192.168.2.1
I did this, and set mine up in Bridge Mode, and all works.
Have you tried setting it up your router / modem in bridge mode? I had to set mine up in bridge mode before everything functioned well.
What is the IP address of your cable modem? Is it the same as the IP on your RT-AC66U?
Are you trying to use the same IP address on the RT-AC66U as you had on your Linksys (default 192.168.1.1)?
Try changing the IP of the RT-AC66U to something else like 192.168.2.1
I did this, and set mine up in Bridge Mode, and all works.
