I have setup on Network>DHCP Server>DNS Server1 & DNS Server2 my preferred DNS servers(DNSFORFAMILY). And yes with this all my devices on LAN use this DNS by default. However, my son has a laptop which he is an admin and so can change the DNS. I sure on his cell phone he can also change is DNS. In order to prevent this, i understand i have to block port 53? This is based on what i have read in several forums. Anyways on my archer C20 v5.0(0.9.1 4.17 v0001.0 BUILD 200915 REL.56357n(5553)) i cannot find a way to add a firewall rule for this specific port. I just don't this as an option on any screen i have seen...unless i am missing something. Any ideas on how to achieve this on ARCHER C20?