Allen-Bradley 1756-CNB Communications Bridge Ethernet ControlNet

Allen-Bradley 1756-CNB is a ControlNet bridge module for Rockwell Automation's ControlLogix system that bridges an Ethernet/IP network to a ControlNet network, enabling data exchange between EtherNet/IP devices and ControlNet I/O without replacing existing hardware. Installed in a 1756 ControlLogix chassis, the CNB provides a dedicated ControlNet channel identified by a Channel Port ID and supports bridging to ControlNet devices across the network, with optional Network Access Port (NAP) support that expands topology options. The module is available in CNB and CNBR variants (including E and CNBR/E for Ethernet-enabled redundancy) to fit different configurations, and is designed to work with Series B and Series E hardware families. Typical applications include connecting older ControlNet I/O to modern Ethernet/IP networks for centralized monitoring and control in manufacturing or process automation. The 1756-CNB supports a substantial number of ControlNet connections—about 40–48 per module—making it suitable for mid-size ControlNet networks.