If you are using a VOIP provider, then you will have to configure your firewall correctly in order to get reliable results. Your firewall must support STATIC PORT MAPPING.

3CX Phone System needs the following ports mapped on the router or firewall to operate properly:

• Port 5060 (TCP and UDP) – Used for SIP protocol transmission – must be a static mapping, no port translation
• Port 5090 (TCP and UDP) – Used for 3CX tunnel (if tunnel is enabled)
• Port 9000-9049 (UDP) – Used for RTP protocol for incoming and outgoing calls
• Port 10000 (UDP) – Used for inbound faxes coming from a VoIP Provider

For business grade results you will also need a static/dedicated IP. Note that many cheap routers do not correctly port forward, and this will lead to problems when making calls. Run the firewall checker if in doubt.

Configuring the Linksys WRT54GC wireless router

1. Login to the web interface of the router using a web browser. E.g. if the router IP is 10.172.0.1, using a web browser access the following URL: http://10.172.0.1
2. Click on the tab “Applications and Gaming”.
3. Click on the tab “Port Range forwarding”.
4. If the PBX internal IP is 10.172.0.119, then configure all specified ports to point to IP address 10.172.0.119. The screenshot below shows how the configuration should look like:

The PBX is now set to receive both incoming and outgoing calls. Run the firewall checker to check that the configuration is OK. For 3CX Phone System to function properly, make sure all specified ports are used solely from 3CX Phone System.