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    How to Block DNS Requests from LAN Devices?

    Scheduled Pinned Locked Moved DHCP and DNS
    13 Posts 4 Posters 4.1k Views
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    • N
      Nonsense
      last edited by

      I would like to prevent any computer clients on my LAN from using DNS's that they may specify and instead use only the ones I have configured on my pfSense router, even if the client has requested a different one.  Does pfSense allow this functionality? It would seem to me to be an essential security feature that should be included with Dynamic DNS.  I am using Internet Guide on DynDNS to filter out categories of websites, but if I change the DNS server on a local machine it overrides the DNS servers set in pfSense. Can I somehow force all requests to only go through the DNS servers that I specify on my pfSense router?

      ???

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      • pttP
        ptt Rebel Alliance
        last edited by

        If you are using pfSense as DNS Server for your LAN (DNS Forwarder enabled), just create a FW rule Blocking TCP/UDP port 53 !LAN Address

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        • N
          Nonsense
          last edited by

          Could you please explain how to do that (assume nothing)?

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          • pttP
            ptt Rebel Alliance
            last edited by

            Is the pfSense the LAN users DNS ?

            Please post a screenshot of your FW LAN rules

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            • N
              Nonsense
              last edited by

              Yes (if I understand you correctly).  I have not created any rules that were not present in the default settings.

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              • pttP
                ptt Rebel Alliance
                last edited by

                Please post a Screenshot of your LAN Firewall Rules (you can attach the img in "aditional options")

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                • pttP
                  ptt Rebel Alliance
                  last edited by

                  Just create a rule as the ones from the attached screenshot, and "put" above any "pass" rule.

                  Is really difficult to help you without knowing (see) your FW rules.

                  Block_Ext_DNS.PNG
                  Block_Ext_DNS.PNG_thumb

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                  • pttP
                    ptt Rebel Alliance
                    last edited by

                    Ok, the rule from my previous post should work, just make sure that it is above the Default allow LAN to any rule

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                    • N
                      Nonsense
                      last edited by

                      Thanks–I'll give it a try.

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                      • N
                        Nonsense
                        last edited by

                        Oops!  The rule appears to work–with one major problem:  I am assigning fixed IPs to my client computers, so I must specify my pfSense router address in each client--the rule also appears to block this (local LAN) address and, as a result, my clients can't talk to the router!  Is there a way I can make an exception to the rule so it does not block the pfSense router address?

                        :(

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                        • johnpozJ
                          johnpoz LAYER 8 Global Moderator
                          last edited by

                          That rule posted would only block access to tcp/udp 53 that is NOT your pfsense lan address.

                          It would not block access to your pfsense lan address on 53, and then your next default allow rule would allow access to everything that is not based on 53 port

                          You setting static IPs on devices has nothing to do with anything.

                          Post your lan rulesetup up again.  So we can see what you did wrong.

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                          • N
                            Nonsense
                            last edited by

                            Ah, I tried the setup quickly, early this morning, when I was in a rush.  I retried it again and discovered that I had neglected to configure the "destination" changes in the rule this morning.  It appears to be working now–I'll find out if it still works the next time I reboot pfSense.  Thanks ptt and johnpoz.

                            :)

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                            • Z
                              ZPrime
                              last edited by

                              @Nonsense:

                              Ah, I tried the setup quickly, early this morning, when I was in a rush.  I retried it again and discovered that I had neglected to configure the "destination" changes in the rule this morning.  It appears to be working now–I'll find out if it still works the next time I reboot pfSense.  Thanks ptt and johnpoz.

                              :)

                              Bad network admin.  Fixed/hardcoded IPs on clients are bad juju.  pfSense can do DHCP reservations - use them.  DHCP makes your life much easier.  Why do you want your life to be difficult?  ;D

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