Recently my Asus RT-AC66U became unable to connect to the internet and whenever I turn it on, the LAN LEDs (#3&4) are solid when nothing is plugged into the LAN ports at all. LAN 1 and 2 seem to always be dimly lit as well and I can't remember if that's the normal state, or that means something too. LAN 4 seems to blink whenever my computer is plugged into any of the LAN ports, but I find my computer is unable to communicate with the router using the hard connection. Wireless seems to work...
RT-AC66U has solid LAN LEDs (3&4) and no internet access
RT-AC66U has solid LAN LEDs (3&4) and no internet access