Creating FQDN With Split DNS
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Creating FQDN With Split DNS

Creating FQDN with split DNS

Creating FQDN with split DNS

Introduction

Prerequisites

Step 1: Create an External FQDN

Test your DNS Entry

Step 2: Create an external FQDN internally

Enable the DNS Role

Add a New Zone

Adding a New Host

Test your DNS Entry

Introduction

3CX Phone System requires that you have an FQDN that resolves externally from outside your network and also internally from within your network. This is required so that internal extensions, remote extensions, internal and remote phone provisioning, VoIP providers and WebRTC calls can reliably work on your PBX using a single FQDN.

To achieve this you create two zones for the same domain, one to be used by the external network the other used by the internal network, typically known as Split DNS.

  • In addition an external FQDN is also required for the creation of your SSL certificate used to secure your connection to the 3CX Phone System and 3CX WebRTC Gateway.
  • You must have a registered domain name.
  • A DNS Server in your local lan (Windows Server or any other configurable DNS Server)

There a two steps you will need to take in order to create your FQDN for your 3CX Phone System.

  • Step 1: Create and configure your External FQDN with your registered domain name
  • Step 2: Create and configure your external FQDN internally (Split DNS).

Step 1: Create an External FQDN

Note: This example is based on EuroDNS. The procedure will 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 “example.com”. 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 hostname. 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 “pbx.example.com” 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.

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.com
  3. As a result you should get the IP Address of the host – in this example: 212.212.212.255

This concludes the creation of your external FQDN, you can now move on to the creation and configuration of your internal DNS.

Step 2: Create an external FQDN internally

This following guide will explain how to create and configure your external FQDN on a Microsoft Windows 2012 R2 DNS Server that is inside your network.

If you do not already have a DNS server created on your network you can create one by following these steps:

Enable the DNS Role

add roles

  1. From your Windows 2012 server, start “Server Manager”
  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.

Once you have created your DNS Server you can now continue to create your Split DNS Zone and records.

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”.
  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”.

  1. Fill in your zone name. In our example we used “example.com”. Click “Next”.
  2. In the Zone File page leave the default options selected and click “Next”.
  3. In the Dynamic Update page leave the default options selected and click “Next”.Click “Finish”.

Adding a New Host

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

  1. Right click on the zone you have just created and select “New Host (A or AAAA)…”.
  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.com” was added. Click “OK” followed by “Done”.

This is the FQDN you will use during the 3CX Phone System Setup in the 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: 192.168.9.71

This concludes your configuration of your Split DNS infrastructure, you can now install and configure your 3CX Phone System using a single external FQDN.

Note: Accessing your external domains from inside your network may be affected after you create your split DNS.

For example, access to your company's website, i.e. www.example.com, may not work from within your network. In which case you will need to add an A record with the external IP Address for each of the subdomains that you need to access from inside your network.

See also the following pages for for more Information:

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