Industrial control systems are complex, software-intensive systems that manage mission-critical production processes. Commissioning such systems requires installing, configuring, and integrating thousands of sensors, actuators, and controllers and is still a largely manual and costly process. Therefore, practitioners and researchers have been working on ``plug and produce'' approaches that automate commissioning for more than 15 years, but have often focused on network discovery and proprietary technologies. We introduce the vendor-neutral OpenPnP reference architecture, which can largely automate the configuration and integration tasks for commissioning. Using an example implementation, we demonstrate that OpenPnP can reduce the configuration and integration effort up to 90 percent and scales up to tens of thousands of communicated signals per second for large Industrial Internet-of-Things (IIoT) systems. OpenPnP can serve as a template for practitioners implementing IIoT applications throughout the automation industry and streamline commissioning processes in many thousands of control system installations.