How to Create an FQDN to 3CX Phone System that resolves locally

3CX Phone System requires that you have an FQDN that resolves locally. When a host is added to your DNS, a mapping is created between the domain and the IP Address of the Host. This guide will explain how to configure Microsoft DNS on Windows Server 2012 R2 to do this.


  • A DNS Server in your local lan (Windows Server or any other configurable DNS Server)

Step 1: Enable the DNS Role

  1. Start “Server Manager”.add roles
  2. Click “Manage” on the top right of the Server Manager window and from the drop-down menu select “Add Roles and Features”.
  3. The Add Roles and Features Wizard will open. Click “Next”.
  4. Leave the default “Role-based or feature-based installation”. Click “Next”.
  5. Select the server that you wish to install the new role on. Click “Next”.
  6. Check “DNS Server” from the list. In the dialog window that pops up, leave the default settings selected and click “Add Features”. Click “Next” to proceed.
  7. On the Features page, click “Next”.
  8. On the DNS Server page, click “Next”.
  9. Click “Install”.
  10. When the installation is completed click “Close” and proceed to the next step.

Step 2: Add a New Zone

From the Server Manager application:

  1. Click “Tools” on the top right on the Server Manager window and from the drop-down menu select “DNS”.new zone
  2. The DNS manager will open. Right click on your server’s name and select “New Zone…”.
  3. The New Zone Wizard will open. Click “Next”.
  4. Leave the default “Primary zone” selected and click “Next”.
  5. Select “Forward lookup zone” and click “Next”.new zone wizard
  6. Fill in your zone name. In our example we used “example.local”. Click “Next”.
  7. In the Zone File page leave the default options selected and click “Next”.
  8. In the Dynamic Update page leave the default options selected and click “Next”.
  9. Click “Finish”.

Step 3: Add a New Host

Your newly created zone will now appear under Forward Lookup Zones:new host

  1. Right click on the zone you have just created and select “New Host (A or AAAA)…”.new host dialog
  2. Fill in the name of the host. In our example we used “pbx”.
  3. Fill in the local IP of the 3CX Phone System machine.
  4. Click “Add Host”. A dialog will appear confirming the that the record for “pbx.example.local” was added. Click “OK” followed by “Done”.

This is the FQDN you should use in the 3CX Phone System Setup in the Internal FQDN Section.

Test your DNS Entry

To make sure that your DNS Server resolves your FQDN to the correct IP Address do the following:

  1. Open a command prompt window on a computer in your lan.
  2. Type in nslookup followed by your domain name – Example nslookup pbx.example.local
  3. You should get as a result the IP Address of the host – in this example:

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  1. Chris McCune

    Hi. What do we do with installations that only have Windows 7 or 8 machines?


    December 11, 2014 at 2:39 pm
  2. @Chris
    Every network must have a DHCP Server and a DNS Server.
    If you do not have a server that does DHCP or DNS, then it means that these services are handled by your router.

    However in this scenario, you would need to run your own DNS server so you need to find a product on windows or a box, that will be on all the time and all DNS queries on your home network will go through it.
    This box needs a fixed IP on your home subnet. Make sure it can’t get bulldozed by DHCP, and your DNS machine itself should not be getting an IP via DHCP. If your DHCP is configured to hand out addresses from to for example, then give your DNS server the IP In the usual situation of home routers you just need to simply tell the router that the DNS server is and reboot.

    December 11, 2014 at 6:14 pm
    • Chris McCune

      Thanks. That makes sense. Chris

      December 12, 2014 at 12:21 am
    • Bryan

      Do you have any other instructions on how to create a internal FQDN for a system that is running windows 7 pro? I do not quite understand how to create an internal FQDN. Thanks

      January 28, 2015 at 12:22 am
    • @Bryan – just skip it and put the internal ip address in the installation dialog.. Everything will work for you.

      January 28, 2015 at 10:35 am
    • Bryan

      Thank you

      January 29, 2015 at 7:46 pm
    • Bryan

      I have installed now but can not get the WebRTC gateway to register. I have a External FQDN but I am using our local static IP for the internal IP. Am I doing something wrong?

      February 2, 2015 at 9:10 pm
    • @Bryan
      WebRTC calls work only from External locations. The Gateway will register when incoming calls are received. Please open a support ticket if this does not work out of the box.

      February 3, 2015 at 11:51 am
  3. complex1

    After reading this article and for the curiosity I’ve add a DNS Server package to my Synology.
    Synology and 3CX PBX (on W7 machine) are running with a locally set IP, phones getting there IP from the router DHCP. These IP’s are fixed by “Bind IP to MAC” (Draytek)
    The DNS Server is setup with a Forward- and Reverse zone.
    In the router, the Synology IP is in the LAN Primary DNS IP-address, leaving the Secondary DNS IP-address empty, so all DNS requests are forced to and handled by the local DNS Server.
    Nslookup and ping are giving the right results, so the DNS Server is setup correctly, I think.

    In 3CX >> Settings >> Phone Provioning >> Internal/Local IP Address field, is filled with the local FQDN (pbx.example.local), then Apply, OK.
    The phone provisioning files are changed (date/time) but when I check the content of it, I noticed that the local address of the PBX is still an IP-address instead of the internal FQDN pbx.example.local.
    Is this a bug, is this by design or do I miss something?
    If this is by design, then what is the use of using a DNS Server?

    Thank you.

    Kind regards,

    December 14, 2014 at 12:16 pm
    • @Complex1 – First and foremost, we force local FQDN configuration for HTTPS. HTTPS makes sense only with FQDN’s and not with IP Addresses.
      Now for the phone provisioning yes you are correct – for the time being the IP Phones (Deskphones) are set to use the local IP Address instead of FQDN. This is because not all phones support HTTPS provisioning.
      However the configuration of the FQDN you made is not for nothing.
      A) We are moving to push the manufacturers to support HTTPS Provisioning in the local lan. So in the future this is going to happen for sure.
      B) 3CXPhone Clients use this local FQDN for MyPhone Presence Connection so it is required. And this is done via HTTPS.
      C) An FQDN is always easier and more user friendly to remember than an IP Address.
      So conclusion, the above are all valid reasons of using a DNS server. Apart from the fact that ALL Networks Must have a DNS Server. The local is not required in a small or home environment. But production systems must be configured for HTTPS and this is the key factor why we enforce users to configure LOCAL DNS and have a local properly resolvable Internal FQDN…

      December 14, 2014 at 1:44 pm
    • complex1

      @Nicky – Thank you so much for your explanation.
      I am happy now.

      December 14, 2014 at 3:17 pm