The Allen Bradley 1756-EN2T is a ControlLogix EtherNet/IP communication module. It acts as a bridge, enabling high-speed communication between ControlLogix controllers and other devices on an Ethernet network. It supports EtherNet/IP communication at 10/100 Mbps and features two Ethernet ports for redundancy. The module also supports features like Device-Level Ring (DLR) for network redundancy and security features for authorized access.