Can knowing only the FQDN/port of 3CX and the MAC address of a phone help to guess its provisioning URL?

Knowing only the Fully Qualified Domain Name (FQDN) and port of the 3CX system, along with the MAC address of a phone, does not provide enough information to accurately guess its provisioning URL. The provisioning URL typically requires more specific data, including additional path information that specifies the model and type of device, as well as the exact provisioning method used by the system.

In 3CX, the provisioning URL is generally constructed based on the PBX's web server address, but it also includes specific parameters that depend on the settings configured within the 3CX management interface. This includes information about the specific phone model and any customization or configuration options that are particular to a user's deployment.

While the FQDN and MAC address form part of the information needed for provisioning, they alone do not yield the complete URL. The provisioning URL can also vary based on the firmware version of the phone, any security measures in place such as HTTPS, or specific directories set up in the 3CX environment. Without access to the 3CX system or knowledge of these configurations, it is not possible to guess the URL successfully.

Thus, simply having the FQDN, port, and MAC address does not suffice to determine the provisioning URL.