Ensure 3CX Phone System Does Not Revert to the Free Edition

3CX Phone System relies heavily on a properly configured network. It is very important that the machine you run 3CX Phone System on is not used for other network related services. The following guide outlines some configuration requirements to ensure that 3CX Phone System does not revert to the FREE Version.

Firstly make sure that your are not installing 3CX Phone System on a machine that has:

  • DNS – A DNS Server takes all available ports on the local host and may result in no available ports for Audio for example.
  • MS SharePoint or Exchange
  • VPN software – A VPN software changes the network configuration and priority of Windows with each incoming connection. This means that when 3CX asks Windows what is the best network route, the VPN software will have a negative impact and Windows may return with a wrong route to 3CX. License issues and Audio Problems are guaranteed.
  • RRAS installed (Inbound or Outbound) – Routing and remote access requires specific network configuration on the local host which makes any networking software impossible to operate. Routing and remote access can only be used if you have a VoIP provider that has provided you with a box to connect to their intranet.

VPN Connections and Licencing Issues 

You should never install 3CX Phone System on a machine that is being used as a VPN Server or has any VPN software installed. If you need to use VPN Software, the solution is to install it on a separate machine which is used only to accept VPN Connections. Once you connect to that machine, then you can access any services in your network from that machine.

When VPN connections are initiated, the IP address that is assigned to the machine together with the mac address changes with each incoming connection. Another major problem is that the priority of the network stack inside Windows becomes dynamic and this results in an unpredictable mess with the routing of your PBX.

When this happens, 3CX will experience licensing issues because 3CX will attempt to communicate to the 3CX ERP from a different network card than the one it previously used at activation stage. (This happens because the VPN Adapter has re-configured the whole network stack prioritization and the interface that was Primary at the moment of activation is now not the primary one any more so traffic is leaving the machine from a different network). This will make 3CX Phone System revert to the FREE Edition causing a license limit to be enforced.

Multiple Network Adapters

NIC Order

In most cases we suggest not to install 3CX Phone System on a machine which has dual network cards. Having said this there are some cases where this is acceptable providing you adhere to the following:

  • One active network interface MUST have a default gateway configured. It is not recommended to have multiple network interfaces all with default gateways configured.
  • Prioritize the network interface used for SIP to the first position from: Control Panel > In the search box type: adapter > Click “View network connections” > Press the “Alt” key, to reveal the menus, and select “Advanced” > “Advanced Settings” > “Adapter and Bindings” tab. From the connections section, Choose your network adaptor that is being used for SIP communication and using the arrows on the right, make sure that it is the first interface in the list.


  • Ensure that all power saving options for your System and Network adapters are disabled (Set the system to High Performance).
  • Disable Bluetooth adapters if it is a client PC.

As you can see there are some very basic requirements that if followed you can insure that 3CX Phone System operates smoothly allowing you to concentrate on what’s important, like delivering the services that your company requires without interruption.

Also take a look at these guides:

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