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

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Create an External FQDN

Test your DNS Entry


3CX Phone System requires you to have a resolvable external FQDN. This is used so that remote extensions, remote phone provisioning and VoIP providers can reliably work on your PBX. Creating an FQDN is also required for the creation of your SSL certificate used to secure your connection to the 3CX Phone System.


  • Your 3CX Phone System server must have a static public IP address.
  • You must have a registered domain name.

Create an External FQDN

Note: This example is based on EuroDNS. The procedure might vary for a different registrars.

  1. Log in to your account.
  2. Navigate to “Control Panel”“Zone Profiles”.

add zone provile - Copy

  1. Click “Add Zone Profile”.
  2. Click “Rename Zone Profile” and give your profile a name. In our example we used “”. Click “Rename” to save your profile name.
  3. Click “Add DNS Record” and select “A (IPv4 Address)” from the menu.

add a record

  1. In the “Host” field fill in your desired host name. In our example we used “pbx”.
  2. In the “IP Address V4” field enter the public IP of your machine.
  3. In the TTL field, leave the default value of 3600.
  4. Click ✓ to save. Your “” FQDN should now correctly resolve to your server’s public IP address.

Note: Your FQDN will not resolve to your server’s public IP address right away. DNS changes usually take 24 hours to take effect.

This is the FQDN you should use in the 3CX Phone System Setup in the External 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
  3. As a result you should get the IP Address of the host – in this example:

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