I have a firewall that is setup but need to have all users inside the network to use a preset dns server. While I know that I can set up this in the DHCP it does not stop a user from changing it in the computer. Is there a way to set up a NAT rule that will cause all DNS requests to be redirected to a set outside DNS server?

  • 4
    Why don't you simply block all outgoing DNS but to the server you need?
    – Zac67
    Sep 22, 2018 at 20:59
  • Welcome. What kind of equipment do you have? I know pfsense does something like what you want, though as Zac says, is there a reason you can't block all non-approved? What problem are you solving?
    – jonathanjo
    Sep 22, 2018 at 21:30
  • We use cisco for a outside dns server to controll content that can be seen. The problem I have is if anyone changes the computer dns to say google it bypasses the cisco filtering. The units that we are using are Sonicwall TZ205W.
    – nick
    Sep 23, 2018 at 3:09
  • As Zac has suggested, you can allow DNS to your approved DNS servers, and then block DNS to any other DNS servers. That has no affect on people using IP addresses or host files.
    – Ron Maupin
    Sep 23, 2018 at 23:10
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Dec 25, 2018 at 9:35

1 Answer 1


If I were trying to accomplish this, I would set an outgoing firewall rule to allow DNS to those specific whitelisted servers, followed by a second rule to block all DNS.


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