@Carl I Cant fnd the System parameters in my archer c20. At times i get a 100Mbps full duplex and at times half. I think there is a negotitation issue between my modem and this router connected...

I bought a new Archer C20 and set it up as Range extender. It was showing both 2.4 and 5 Ghz wifi but I once restarted it and then it stopped broadcasting 5Ghz wifi. What do I do? I have read threads...