Allen-Bradley 1756-CNB ControlLogix Communication Module

The Allen-Bradley 1756-CNB is a ControlLogix ControlNet Bridge Communication Module (Catalog No. 1756-CNB) that provides a ControlNet interface to a ControlLogix controller, serving as the bridge between the processor and a ControlNet network to reach remote I/O and devices. It is part of the 1756 ControlLogix product family and is installed as a communications module in a ControlLogix chassis, enabling data exchange between the local controller and distributed I/O over ControlNet. As of December 31, 2024, Rockwell Automation has announced that the 1756-CNB is discontinued and no longer available for sale; remaining stock is typically through surplus or remanufactured vendors. In practice, this module is used in automation environments that rely on ControlNet to connect remote I/O racks to a ControlLogix system, facilitating mapped data transfers and synchronization across the ControlNet network.