I just recently purchased an Asus RT-AC86U and connected it behind my internet provider's modem then I had a lot of problems in connecting all of my devices. After repeatedly hard resetting the Asus router and reconfiguring it again, all my devices would connect successfully. But after a few minutes (sometimes hours) some devices (not all) would not be able to connect anymore despite resetting the devices, forgetting the SSID and then reconnecting again. My final solution was to define the devices' MAC on the router and manually assign an IP address. After this I never had connection problems anymore, but my concern is it did not really solve the DHCP problem. Some new devices trying to connect via DHCP is still failing and the IP address 7.15.xx.xx is displaying on those devices. I am not a networking expert, may I ask for some help/advices on how to solve this? Thanks.