Model : Archer D7

Hardware Version : V1.1

Firmware Version : 0.9.10.9 v002d.0 Build 141014 Rel. 51158n

ISP :

Initially I had an ADSL connection and the Archer D7 worked perfectly as an ADSL moder/router, WiFi speeds on both bands were great too.

Then I upgraded to a 100 Mbps fibre connection and switched the operation mode of the Archer D7 over to a wireless router only. My internet speeds - download and upload - are on par via a CAT 5E cable but suddenly my WiFi speeds are woeful to say the least (far worse than previously). My current settings are (same as before):

2.4GHz band - 11 b/g/n mixed, channel 1, 20 MHz; 5GHz band - a/n/ac mixed, channel 161, 40 MHz.

Any help would be greatly appreciated!

UPDATE: Out of desperation I downloaded and installed the latest firmware for my router and my WiFi woes have been resolved.