Login to your 3CX server, and navigate to 'SIP Trunk', located on the left hand menu
Select "Add SIP Trunk" and complete the following fields;
On the "Generic SIP Trunk" page, on the General tab, modify the following fields, copying the details from the SIP Trunk
Note: Depending on your 3CX version, you may need to disable 'Auto Discovery' on this page.
Select the Options tab and modify the following fields:
Note: Configuration of other 3CX features and settings on this page, such as DID routing, are outside of the scope of what synex can support and you should refer to the 3CX support documentation.
From the "SIP Trunks" page, click "Enable All". If details have been entered correctly and your 3CX server is connected to the Internet, 3CX will register and the status icon on the newly created SIP Trunk will change to green.
We also recommend you whitelist our primary SIP server's IP address within 3CX, to prevent accidental blocking and subsequent registration issues. For information on how to perform this step, please see https://support.synex.com.au/en/knowledgebase/article/3cx-suddenly-loses-sip-trunk-registration
In order to make calls, you may need to configure "Outbound Rules" to route calls via SIP Trunk. You should refer to the 3CX support documentation for details.