cereberus said:
You need to set up second router by connecting lan on main router to wan port on second router.

Then connect tablet to second router.

Connecting LAN to LAN will not work unless dhcp is disabled on second router. Problem then is internet gateway is on primary router and you will struggle to use parental control.

By connecting LAN to WAN second router is behind a NAT firewall , and when tablet connects to second router, you can use parental controls independently of lan on primary router.

The IP address of 2nd router has to be on a different subnet e.g. if main router is 192.168.0.1 the second router needs a different 3rd digit e.g 192.168.1.1.

I suspect both routers are on same subnet by default (same 3rd number) and that is why you are having issues.
Megahertz said:
Thanks cereberus.

I'm not at home ATM but will try as soon as I return.
- I will set the IP address of the Archer C21 (the one with parental control) as 192.168.2.9 (today it's 192.168.0.9) and the Cable modem router is 192.168.0.7
- I will connect the Cable modem router LAN port 1 to the WAN port of the Archer C21

What about the IP the Archer C21 assigns to the clients? Now it's 192.168.0.21 to 192.168.0.30. Should I also change to 192.168.2.21 to 192.168.2.30?
Working fine. Thanks