Allen-Bradley 1756-EN2TR/B Upgrade Solution for ControlLogix

Product Overview

Allen-Bradley 1756-EN2TR/B Upgrade Solution for ControlLogix: Seamless Migration from Legacy EtherNet/IP Systems

The Allen-Bradley 1756-EN2TR/B is a dual-port EtherNet/IP communication bridge module designed for the ControlLogix 1756 platform. It supports Device Level Ring (DLR) topology, enabling fault-tolerant ring network architectures without an external managed switch. For facilities running aging 1756-EN2T, 1756-EN2TR/A, or first-generation 1756-ENBT modules, the 1756-EN2TR/B represents a direct, low-disruption upgrade path that preserves existing wiring infrastructure, rack geometry, and RSLogix 5000 / Studio 5000 program logic.

Industrial sites operating legacy ControlLogix systems frequently encounter obsolescence challenges: discontinued firmware support, unavailable spare parts, and increasing network latency caused by older single-port EtherNet/IP bridges. The 1756-EN2TR/B resolves these issues by providing a hardware-compatible replacement that slots directly into any 1756 chassis — including the 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17 rack sizes — without requiring chassis modification or additional backplane adapters.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful migration from a legacy ControlLogix EtherNet/IP architecture to the 1756-EN2TR/B typically involves coordinating several interdependent components. During pre-migration assessment, engineers should verify the firmware revision of the resident 1756-L71, 1756-L72, 1756-L73, or 1756-L74 ControlLogix controller, as the 1756-EN2TR/B requires a minimum controller firmware version for DLR supervisor functionality. In most brownfield installations, a firmware update to the controller is the only software-side change required before swapping the communication module.

On the I/O side, remote I/O racks connected via 1756-EN2T or 1756-ENBT adapters — such as those using 1756-IB16, 1756-OB16E, or 1756-IF8 analog input modules — continue to communicate without modification after the bridge replacement, since the EtherNet/IP implicit messaging structure is preserved. Engineers migrating from a star topology to a DLR ring simply need to connect the second RJ-45 port of the 1756-EN2TR/B to the downstream device in the ring, which may include 1734-AENTR Point I/O adapter modules or 1769-L30ER CompactLogix controllers acting as ring nodes.

For installations where the legacy system used a 1756-DHRIO Data Highway Plus / Remote I/O bridge alongside the EtherNet/IP module, the 1756-EN2TR/B migration is typically staged: the EtherNet/IP network is upgraded first, and the DH+ segment is retained on a separate 1756-DHRIO module in the same chassis. This approach eliminates the need for a full cutover and allows phased commissioning. Similarly, sites using a 1756-CN2 ControlNet bridge module in the same rack can continue operating the ControlNet segment in parallel during the EtherNet/IP migration.

Panel builders and system integrators should also account for the 1756-EN2TR/B’s dual-port cabling requirement when planning control cabinet space. The module’s two RJ-45 ports exit from the front face, and standard 1756 module keying applies. In tight enclosures, right-angle RJ-45 patch cables are recommended to maintain bend radius compliance. The module draws power from the 1756 backplane; no separate 24 VDC field power is required, simplifying the power distribution design within the cabinet.

For sites requiring a programming connection during commissioning, a standard Ethernet patch cable from a laptop running Studio 5000 Logix Designer to the plant network — or directly to the module’s port — is sufficient. No dedicated 1784-U2DHP USB-to-DH+ programming cable is needed for EtherNet/IP-based controllers, which further reduces tooling requirements during the retrofit.

Retrofit Guidance FAQ

Q: Can I replace a 1756-EN2T with the 1756-EN2TR/B without modifying my Studio 5000 project?
A: Yes. The 1756-EN2TR/B is recognized as a compatible module in Studio 5000. You can update the module profile in the I/O tree by right-clicking the existing 1756-EN2T entry and selecting “Change Module Type” to 1756-EN2TR. The IP address, connection parameters, and tag structure are preserved. A controller download is required to apply the change, but the program logic itself does not need to be rewritten.

Q: Does the second Ethernet port on the 1756-EN2TR/B need to be connected?
A: No. If you are not implementing a DLR ring, the second port can remain unused. The module operates normally as a single-port EtherNet/IP bridge in this configuration, making it a drop-in replacement for the 1756-EN2T with no topology changes required.

Q: What is the wiring difference between the 1756-ENBT and the 1756-EN2TR/B?
A: The 1756-ENBT uses a single RJ-45 port with a BNC connector for legacy coaxial connections on some revisions. The 1756-EN2TR/B uses two standard RJ-45 ports only. If your existing installation uses the BNC port, you will need to transition to a standard Cat5e/Cat6 Ethernet connection, which is standard practice in any modernization project.

Q: Is the 1756-EN2TR/B compatible with older 1756 chassis and power supplies?
A: Yes. The module is fully compatible with all standard 1756 chassis sizes and the 1756-PA72, 1756-PB72, 1756-PA75, and 1756-PB75 power supply modules. No chassis or power supply upgrade is required.

Q: How do I configure the IP address on the replacement module?
A: The 1756-EN2TR/B supports BOOTP, DHCP, and static IP assignment — the same methods as the 1756-EN2T and 1756-ENBT. Use the Rockwell BOOTP-DHCP Server utility or set a static address via the module’s front-panel rotary switches. The existing IP address from the legacy module can be reassigned directly to the new module with no network-side changes.

Q: What communication protocols does the 1756-EN2TR/B support?
A: The module supports EtherNet/IP (CIP), including explicit messaging, implicit (I/O) messaging, and DLR ring supervisor/node roles. It does not natively support Modbus TCP or PROFINET; those protocols require a separate gateway if needed in a mixed-protocol environment.

Warranty Assurance

Every 1756-EN2TR/B unit shipped by TOPNLMS is covered by a 12-month warranty from the date of delivery. Prior to shipment, each module undergoes functional verification including backplane communication testing, port link integrity checks, and firmware version confirmation. Units are packaged in anti-static ESD bags with foam cushioning to prevent transit damage.

In the event of a confirmed hardware defect within the warranty period, TOPNLMS will arrange a replacement unit or issue a full refund, subject to return inspection. Our technical support team is available to assist with installation questions, firmware compatibility queries, and commissioning guidance via email at [email protected] or by phone at +86 18359293191.

We maintain in-stock inventory of the 1756-EN2TR/B and related ControlLogix spare parts to support urgent replacement requirements. Orders confirmed before 3:00 PM CST on business days are typically processed for same-day dispatch. International shipping to Southeast Asia, the Middle East, and Europe is available with full export documentation support.

TOPNLMS is committed to providing reliable, spec-accurate industrial automation components to B2B buyers who require fast turnaround, verified quality, and post-sale technical support. Our procurement team can assist with multi-unit orders, consignment stock arrangements, and cross-reference verification for discontinued Rockwell Automation part numbers.