@MasumAbrar Try using Access Control (Chapter 4.9, pages 44,45,46) for that purpose.

@thedirtyshoe I believe that TL-WR841N still supports that feature.

@Bobking The topology - use the blue/Internet port of C6 for an uplink to your main router. Try these wireless settings and see if any difference: For the 2.4 GHz band do the same but Mode: 802.11n...

@Freespoola I would go for the dedicated AP.

@ItsMillerTime79 These are mine:

@Shipwreck Make sure your wireless settings look like this: Do the same for 2.4GHz band (except MIMO will be missing there). As for the QoS disabling you should uncheck the box in the screenshot...