Q: What are the practical benefits of the dual-port DLR ring network function of the 1756-EN2TR? How to configure redundancy?
A: DLR (Device-Level Ring Network) is a key technology for network redundancy. In a ring network topology, two ports are connected to form a closed loop. If any point on the ring is disconnected (e.g., due to cable damage or power failure), network communication can be automatically restored within microseconds without interrupting control. During configuration, a device needs to be selected as the ring network supervisor, and the others are ring network nodes. It's important to note that in a redundant control system (master/standby controller), the two EN2TR modules will use the same IP address. The selection of the DLR activity manager is based on the smaller MAC address, not on which is the master controller; this is often misunderstood.
Q: What are the main differences between the 1756-EN2TR and 1756-ENBT? Which one should I choose?
A: The core differences lie in performance and capacity. The 1756-EN2TR is an upgraded version of ENBT, offering double the capacity (EN2TR supports 256 CIP connections, ENBT supports 128) and dual-port DLR support (ENBT only has a single port and does not support ring network redundancy). For new projects, the 1756-EN2TR is strongly recommended; if your existing system uses ENBT and its functionality is sufficient, you can keep the original model.
Q: In which racks can the 1756-EN2TR be installed? Is it compatible with my existing ControlLogix system?
A: Excellent compatibility. This module occupies one slot and can be installed in any standard ControlLogix 1756 series rack (including the 1756-A17, A13, A10, A7, A4, etc. mentioned earlier). It can work with ControlLogix controllers (such as the 1756-L81E), I/O modules, and other communication modules in the rack, exchanging data via the backplane bus. There are no slot position restrictions during installation; it can be flexibly placed according to the system design.
