Allen-Bradley 1756-CNB Communication Bridge Module

The Allen-Bradley 1756-CNB ControlNet Bridge Module is a single-port bridge that links a ControlLogix controller to a ControlNet network, enabling structured data exchange between a central controller and remote devices across one ControlNet segment. In a ControlLogix chassis it provides a dedicated ControlNet interface with a 5 Mbps data rate and supports 40–48 Logix Communications Connections, making it suitable for bridging I/O and produced/consumed data across racks or remote locations. This module is designed for legacy ControlLogix systems and is commonly used to extend ControlNet reach within a multi-chassis architecture, supporting scheduled and unscheduled communications that coordinate control and I/O operations over the ControlNet network. As of December 31, 2024, Rockwell Automation has discontinued the 1756-CNB, so availability is generally through distributors of legacy components; users maintaining existing systems may source replacement units through authorized channels or refurbishment partners.