I just replaced my local 3CX server with one provisioned by Google Cloud Platform with a static IP number. In 3CX-->SIP Trunks-->Flowroute-->Edit-->General, outbound proxy is set to the static IP #; Type of Authentication is set to "Do not require - IP Based; Authentication ID and Authentication...
We use flowroute for a number of our customers and have been extremely happy with it, however we do everything via SIP Registration (An authentication / SIP User ID and Password)
However, flowroute also makes a recommendation on their site to use IP based authentication
After doing a fair...