OpenDNS. How to avoid clients to use another DNS to the ones provided by the router?

[phosphato]

Hi all.

I managed to set my RT-AC66U with DNSOMATIC and OpenDNS. Everything works correctly.

My question is whether you can further adjust the router configuration so that if clients try to use a different DNS, the router will force them to use their own.

I have read about filtering port 53 but I can not get it working.

Can anyone help?

Thank you very much in advance.

 

[RMerlin]

Need a custom firmware to add an extra rule in the firewall - see this Wiki page.

 

[phosphato]

Need a custom firmware to add an extra rule in the firewall - see this Wiki page.

Thanks RMerlin

I am newbbie but I will try anyways...