Siemens is notorious for its complex product naming conventions, and the Modbus licenses are no exception. The license you need depends heavily on the controller family you are using: S7-1200 or S7-1500.
Modbus TCP licensing for Siemens SIMATIC PLCs varies by generation, with no license required for standard communication on modern S7-1200/S7-1500 CPUs, while legacy S7-300/400 units require a chargeable license. Redundant Modbus communication and legacy systems require a hardware-bound license activation process using an IDENT_CODE and REG_KEY . For detailed licensing procedures, visit Siemens Industry Online Support . siemens modbus tcp license
If you are using redundant communication (e.g., S7-400H), you typically need a specific "Modbus/TCP CP Red" or "PN Red" license. 2. Types of Siemens Modbus TCP Licenses Siemens is notorious for its complex product naming