Configuring 3CX with SIP trunks for your business involves a structured sequence of steps, from initial preparation through to testing and optimisation. Before starting, you should confirm that your 3CX version is supported, your licences are valid, and your internet connection and firewall are suitable for VoIP traffic. You will also need SIP trunk details from your chosen provider, including SIP server addresses, authentication credentials, and any required codecs or security settings. Once these prerequisites are in place, you can log into the 3CX Management Console, navigate to the SIP Trunks section, and begin adding a new trunk using either a pre-configured template for your provider or a generic SIP trunk configuration.
During configuration, you will define the main trunk number, assign inbound and outbound rules, and set caller ID formats to align with your numbering plan. It is essential to configure codecs that balance call quality with bandwidth usage, and to ensure NAT and firewall traversal settings are correctly applied so calls can pass reliably in both directions. After saving the configuration, you should thoroughly test inbound and outbound calls, DDI routing, voicemail, and any call queues or ring groups that rely on the trunk. Ongoing monitoring, including reviewing call logs and quality metrics, will help you fine-tune the setup, ensuring stable performance and a scalable foundation for your business communications.
Begin by gathering all technical details from your SIP trunk provider, such as SIP registrar, proxy addresses, authentication username and password, and recommended codecs. Access the 3CX Management Console, go to “SIP Trunks”, and select “Add SIP Trunk”. Choose your provider from the list if available, or use a generic template, then enter the main trunk number and registration details exactly as supplied.
Next, configure inbound and outbound rules so calls are routed correctly. For inbound calls, map DDIs or the main number to the appropriate destinations, such as reception, call queues, or IVR menus. For outbound calls, create rules that define which trunk to use for local, national, mobile, and international calls, and apply any required dial prefixes or number transformations.
Finally, review network and security settings. Ensure firewall ports are open as recommended, confirm STUN or SBC usage if required, and enable secure SIP and SRTP where supported. Test multiple call scenarios, monitor call quality, and adjust codecs, timeouts, and failover options to maintain reliability as call volumes grow.
