May 10, 2016 at 00:07Best Practices: Split DNS (Split DNS) in 3CX Phone System Infrastructure
- Tutorial
- Recovery mode
Introduction
For the correct operation of the 3CX Phone System, it is recommended to configure and use the so-called split DNS (Split DNS). Split DNS uniformly represents the network host names (FQDNs) in the internal and external networks. In other words, the 3CX Phone System server will be available on a private and public network under a single FQDN name. This approach provides several advantages:
- provides uniform configuration of internal and external connections to the server
- accelerates user re-registration when switching from internal to external network and vice versa
- allows you to create the same configuration for internal and external users 3CXPhone
- allows you to administer the system, view reports and listen to recordings of conversations, regardless of user location
- allows you to specify a single auto-tuning URL in IP phones, regardless of their location
To successfully configure Split DNS, a number of conditions must be met:
- creating a self-signed SSL certificate, or purchasing a trusted certificate from an accredited company
- availability of a registered domain name at a domain registrar
- the presence of a static IP address
- Your internal network must have a DNS server running. It can be a DNS based on Windows Server or a DNS server implemented in a firewall.
It is recommended that you create Split DNS before installing the 3CX Phone System server.
Split DNS is created in two stages:
- Configure the DNS zone on the public DNS server at the registrar of your domain name - public FQDN name of the server 3CX Phone System
- A similar zone is created in the internal DNS north - the private FQDN name of the 3CX Phone System server
Public FQDN server name
We show the setting of the public name of the server using the example of the EuroDNS registrar. For other registrars, the procedure is not fundamentally different.
- Log in to your account.
- Go to Control Panel > Zone Profiles
- Click Add Zone Profile
- Click Rename Zone Profile and name the profile. In this example, we used example.com . Click Rename to save the profile name.
- Click Add DNS Record and select A (IPv4 Address) from the menu.
- In the Host field, specify the desired server name. In our example, this is pbx
- In the IP Address V4 field, specify the public IP address of your 3CX Phone System server
- TTL field leave default 3600
- To save the settings, press ✓. An A record (your FQDN server name) pbx.example.com will be created. After some time, which can take up to 24 hours , your public FQDN server name will be converted to a public IP address.
To test that the public FQDN name is configured correctly, at the command prompt, type nslookup pbx.example.com . The command must be executed on a computer located on the external network. In response, you should get the external IP address of the 3CX server.
Private FQDN server name
We show how to configure a private FQDN name on a DNS server located on your company's internal network. The example is based on the Windows 2012 R2 DNS server and assumes that the server is configured from scratch.
Enabling the DNS Role
- Launch Server Manager
- In the upper right corner of the Server Manager window, click Manage and select Add Roles and Features from the drop-down menu.
- In the Add Roles and Features Wizard window, click Next
- Leave the default option Role-based or feature-based installation and click Next.
- Select the server to which you want to assign a new role and click Next
- In the list, select DNS Server . In the dialog that appears, leave the default values, click Add Features and Next
- On the Features page, click Next.
- On the DNS Server page, click Next
- Click Install
- When installation is complete, click Close.
After adding the DNS server role, create a Split DNS zone and records in it.
Adding a New Zone
A new zone is created in the Server Manager snap-in:
- In the upper right corner of the snap-in, select Tools and in the DNS drop-down menu
- The DNS manager will open. Right-click on the server name and select New Zone ...
- In the New Zone Wizard, click Next
- Leave the default primary zone and click Next.
- Select Forward lookup zone and click Next.
- Enter the name of the zone, in our example, example.com , and click Next
- On the Zone File page, leave the default settings and click Next.
- On the Dynamic Update page, leave the default options, click Next and Finish
Adding a new host
The newly created zone will appear in the Forward Lookup Zones section:
- Right-click on the created zone and select New Host (A or AAAA) ...
- Specify the host name, in our example, pbx
- Specify the private (local) IP address of the 3CX Phone System server
- Click Add Host . A message appears stating that the pbx.example.com entry has been created. Click OK and Done
It is this FQDN name that you specify during the installation of the 3CX Phone System server in the FQDN section.
To test that the private FQDN name is configured correctly, at the command prompt, type nslookup pbx.example.com . The command must be executed on a computer located on the internal network. In response, you should get the internal IP address of the server.
Split DNS is created. From now on, the 3CX Phone System will use a single FQDN name on the public and private networks.
Possible problems
Depending on the type of DNS server used, you may find that your other hosts, for example, the web server www.example.com , become unavailable from the internal network. This is due to the fact that your local DNS server will begin to use the internal DNS zone, and not redirect requests from local clients to an external DNS server. In this case, it is necessary to duplicate in the internal DNS zone A records of all hosts located in the external DNS zone. A record must contain the domain name of the host and its public IP address.
