RTN66U and TP-8817 won't work

I'm at my wits end. I've bought 2 seperate modems for this router,one was faulty and the other one connects tothe internet just fine. I connected the working modem "TP-8817" to the router, setup all the settings, yet everytime when it comes to the "detecting internet type again" (Or something along those lines) part of the quick setup, it always throws the error "internet connection type detection timed out|" I have no idea what to do, and I've been trying different settings and resetting the router for around 2 weeks now, any help or information would be incredibly appreciated

In reply to a post by Ozil_416:

EDIT:

I fixed this, Not sure if this will work for you but the issue you have sounds the same as mine... make sure you have also turned off/disabled the DHCP under 'LAN' Setting on the TP-Link TD-8817.

Interface Setup > LAN (Tab) > Disable DHCP

I turned it off and now my TD-8817 and RT-N66U are talking, Happy Days!

Point 1) Reset the TP-8817. All you need to do is change one setting as suggested by BatBoy. Disable DHCP on the TP-8817. The issue you have currently is both are trying to assign IP addresses.

Keep DHCP on the asus enabled.

If this fails...

Point 2) Also ensure the TP-8817 IP address is set to either get the asus IP via DHCP or set in range of the Asus's IP address. Usually 50+ away from the minimum. E.g. say the asus uses 192.168.0.2, 192.168.0.3 etc, set the TP-8817 to 192.168.0.50 at the lowest.

Usually point 2 will just work via DHCP on the asus anyway and needs no fiddling.