Allen-Bradley 1756-EN2TR — EtherNet/IP Module Buying Guide

By Abdullah Zahid
16 min read
Allen-Bradley 1756-EN2TR ControlLogix dual-port EtherNet/IP communication module for industrial automation

Allen-Bradley 1756-EN2TR ControlLogix Ethernet Dual-Port 10/100M Interface Module — Specs, Review & Selection Guide

Controls engineers specifying a ControlLogix EtherNet/IP network that demands ring topology resiliency, motion-capable communication, and a proven dual-port connection budget land on one module more consistently than any other: the Allen-Bradley 1756-EN2TR. This ControlLogix Ethernet Dual-Port 10/100M Interface Module sits in a 1756 chassis backplane, bridges the controller to plant Ethernet over two copper RJ45 ports sharing a single IP address, and supports Device Level Ring topologies that keep communication alive through a single cable or node failure — all within a module rated for operation up to 60 °C. If you are validating technical fit or confirming availability before committing to a BOM, the details below settle both questions.

If you have already confirmed this is the right part, check current pricing and availability for the 1756-EN2TR at LeadTime.ca — ships worldwide.

Who Should Buy the 1756-EN2TR — and Who Should Choose a Different Module

The Allen-Bradley 1756-EN2TR is the right choice for engineers building or expanding a ControlLogix system where EtherNet/IP is the plant-standard protocol and network resiliency through Device Level Ring is either required or strongly preferred. Choose this module when all of the following apply:

  • Your platform is ControlLogix 1756 and the chassis, controller firmware, and Studio 5000 version are confirmed compatible with the 1756-EN2TR series and revision you plan to order.
  • You need dual Ethernet ports with embedded switch function and DLR support — not a single-port module.
  • Copper RJ45 at 10/100 Mbps is acceptable and EtherNet/IP is the protocol in use — no fiber or gigabit requirement exists.
  • Your expected TCP/IP connection load fits within the module's supported limit of up to 128 TCP/IP connections, and your motion requirement is within the supported limit of up to 8 axes over EtherNet/IP.
  • Your plant environment suits the standard 1756-EN2TR — corrosive or high-contamination environments requiring conformal coating belong on the 1756-EN2TRK variant instead.

If only a single Ethernet port is needed and budget is a constraint, the 1756-EN2T is the correct choice. If connection density in a single slot must exceed what the 1756-EN2TR provides, evaluate the 1756-EN4TR. For harsh or corrosive environments requiring conformal coating, specify the 1756-EN2TRK.

On this page:

What the 1756-EN2TR Actually Does in a ControlLogix System

The Allen-Bradley 1756-EN2TR is a dedicated EtherNet/IP communication module — not a controller, not a remote I/O adapter, but a backplane-resident bridge that connects a ControlLogix 1756 chassis to an Ethernet network and handles all EtherNet/IP messaging on behalf of the controller. This matters because it offloads communication processing from the CPU, allowing the controller to focus on scan execution while the 1756-EN2TR manages real-time I/O connections, HMI messaging, drive communication, motion axis synchronization, and information-layer traffic simultaneously.

Two RJ45 ports provide the physical Ethernet connections. Both ports share a single IP address and behave as an embedded switch — they do not act as separate network interfaces, and they cannot be placed on different subnets. This is the most important architectural fact about this module, and it is also the most commonly misunderstood. The dual-port configuration enables two distinct benefits: it allows the module to participate in a Device Level Ring, where one port connects to the upstream ring neighbor and the other to the downstream neighbor, providing automatic ring healing after a single break; and in linear topologies, it allows daisy-chaining between devices without requiring a separate unmanaged switch at every node.

A USB 1.1 device port provides a direct connection point for programming and configuration from a laptop, independent of the Ethernet network. The module is backplane-powered from the ControlLogix 1756 chassis, occupies a single slot, and supports operation up to a maximum ambient temperature of 60 °C.

Typical System Architecture for the 1756-EN2TR

The 1756-EN2TR sits between the ControlLogix CPU on the backplane and the plant EtherNet/IP network, acting as the communication bridge for all Ethernet-connected devices. Here is where it fits in the typical component chain:

  • ControlLogix 1756 chassis — houses the CPU, power supply, and the 1756-EN2TR in an adjacent slot on the backplane.
  • 1756-EN2TR — bridges the backplane to Ethernet; both RJ45 ports connect into the machine-level network or a DLR ring.
  • Managed or unmanaged Ethernet switch (if not running pure DLR) — distributes traffic to downstream EtherNet/IP devices when a star topology is used.
  • EtherNet/IP field devices — remote I/O adapters, EtherNet/IP drives, safety modules, servo drives (up to 8 motion axes per module), and HMI panels connected to the ring or network.
  • Engineering workstation — connects either via the network or directly to the USB 1.1 port on the 1756-EN2TR for programming and firmware management.

Typical Applications and Deployment Scenarios

In automotive and discrete manufacturing, the 1756-EN2TR is the standard communication module for machine cells where ControlLogix CPUs drive EtherNet/IP-connected servo drives, safety I/O, and HMI panels across a DLR ring. A single cable break anywhere in the ring does not interrupt production — the module detects the fault and continues communicating through the surviving path.

Food and beverage and packaging lines frequently use the 1756-EN2TR to connect the ControlLogix controller to distributed I/O and variable-frequency drives over EtherNet/IP. The dual-port DLR capability is especially valued in long conveyor and fill-line architectures where stringing a ring through sequential machines is mechanically simpler than building a star back to a central switch.

In process industries — oil and gas, chemicals, and mining — ControlLogix systems with DCS-style architectures use the 1756-EN2TR to bridge the controller chassis to the plant Ethernet backbone, carrying real-time I/O and information messaging. The module's support for time synchronization makes it applicable in applications where event timestamping is a control or compliance requirement.

Material handling and warehousing installations with large EtherNet/IP device counts — conveyor drives, barcode readers, and distributed safety — depend on the 1756-EN2TR's connection capacity and ring resiliency to meet uptime targets. Retrofit projects replacing legacy 1756-ENBT modules also land on the 1756-EN2TR as the standard upgrade path, gaining DLR capability and higher connection capacity while reusing the existing ControlLogix chassis.

Application Typical Deployment
Automotive assembly cell 1756-EN2TR bridging ControlLogix CPU to servo drives and safety I/O over a DLR ring
Food and beverage packaging line Dual-port daisy-chain or DLR connecting drives, distributed I/O, and HMI along a conveyor
Process plant ControlLogix DCS node Module providing EtherNet/IP backbone link with time synchronization for I/O and information
Material handling / warehousing High-device-count EtherNet/IP network with ring resiliency and up to 128 TCP/IP connections
Legacy 1756-ENBT upgrade Direct slot-for-slot chassis replacement upgrading to DLR capability and higher connection budget
OEM machine export Standard ControlLogix machine with 1756-EN2TR providing the single EtherNet/IP bridge to customer plant network

1756-EN2TR Key Specifications

Specification Detail
Catalog Number 1756-EN2TR
Product Family ControlLogix 1756 Communication Modules
Ethernet Ports 2 x RJ45, 10/100 Mbps copper, auto-negotiation, full/half duplex
USB Port USB 1.1 device port (programming only)
Protocol EtherNet/IP
Dual-Port Function Embedded switch; both ports share the same IP address — not separate subnets
Supported Topologies Linear and Device Level Ring (DLR)
TCP/IP Connections Up to 128 TCP/IP connections
Motion Axes Up to 8 motion axes over EtherNet/IP
Max Operating Temperature 60 °C

Full technical specifications are available on the product page at LeadTime.ca.

1756-EN2TR vs 1756-EN2T vs 1756-EN4TR vs 1756-ENBT — Which Module Do You Need?

Choosing the wrong variant in this family is one of the most common ordering errors in ControlLogix EtherNet/IP projects. The following table maps the key decision points:

Module Ethernet Ports DLR Support TCP/IP Connections Motion Axes Coating Option Notes
1756-EN2TR 2 x RJ45 (embedded switch, shared IP) Yes Up to 128 Up to 8 1756-EN2TRK (conformal) Standard dual-port DLR choice for modern ControlLogix systems
1756-EN2T 1 x RJ45 No Up to 128 Up to 8 Available in coated variant Lower cost single-port module; correct choice when DLR is not required
1756-EN4TR 4 x RJ45 Yes Higher connection density per slot Higher axis count per slot Check availability Step up when a single slot must serve more connections than 1756-EN2TR supports
1756-ENBT 1 x RJ45 No Lower than EN2TR Limited Not available Legacy module; 1756-EN2TR is the standard upgrade path for ENBT retrofit projects
1756-EN2TRK 2 x RJ45 (embedded switch, shared IP) Yes Up to 128 Up to 8 Conformal coated (standard) Specify instead of 1756-EN2TR for corrosive or high-contamination environments

If your system uses a single Ethernet port and DLR is not a requirement, specifying a 1756-EN2T avoids paying for dual-port capability you will never use. If your connection count or motion axis count exceeds what the 1756-EN2TR supports, the 1756-EN4TR is the logical step up — check current availability for all variants at LeadTime.ca.

Expert Verdict: Is the 1756-EN2TR the Right Module for Your Project?

The Allen-Bradley 1756-EN2TR earns its position as the default EtherNet/IP communication module for serious ControlLogix builds. Controls engineers and integrators standardizing on ControlLogix who need a dependable EtherNet/IP bridge with dual-port DLR, a solid connection budget of up to 128 TCP/IP connections, motion support for up to 8 axes, and long-term Rockwell ecosystem alignment will find this module does exactly what it should — without requiring workarounds or external ring-management hardware. Its support for time synchronization extends its usefulness into motion-critical and timestamped-event applications. For plants that value predictable behavior, thorough Knowledgebase documentation, and a proven installed base, the 1756-EN2TR is a low-risk specification decision.

That said, the 1756-EN2TR is not universally the right answer. For cost-sensitive or smaller systems where only a single Ethernet port is needed and DLR topology is not part of the network design, the 1756-EN2T delivers the same protocol capability and connection count without the cost premium of the dual-port hardware. When an installation environment involves corrosive gases, condensation, or contamination levels that exceed the standard module's environmental class, the 1756-EN2TRK conformal-coated variant is the correct specification — not the standard 1756-EN2TR with an expectation it will survive. For legacy 1756-ENBT retrofit projects, the 1756-EN2TR is the natural upgrade target and provides a measurable step forward in DLR capability and connection capacity. Where a single chassis slot must support a connection density or motion axis count beyond what the 1756-EN2TR handles, the 1756-EN4TR is the correct path forward.

From a procurement standpoint, the 1756-EN2TR is often stocked at major distributors worldwide, but like all ControlLogix communication modules, availability is sensitive to Rockwell allocation cycles and project-driven demand spikes. Confirming real-time stock, verifying the firmware series on the unit in stock against your controller firmware, and having a specialist check BOM compatibility before ordering removes the primary risk factors that delay ControlLogix commissioning projects. A specialist distributor familiar with ControlLogix module families can also flag when an alternative series or variant is a better fit — saving time and preventing expensive rework. View current availability and pricing for the 1756-EN2TR at LeadTime.ca.

For volume pricing, confirmed lead times, or to discuss your full ControlLogix BOM before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

What Engineers Report After Deploying the 1756-EN2TR

Across PLC forums including PLCTalk, PLCS.net, MrPLC, Reddit r/PLC, Reddit r/automation, and Rockwell's own Knowledgebase discussion threads, the Allen-Bradley 1756-EN2TR carries a consistently positive reputation among experienced ControlLogix engineers. The phrase that recurs most often is some variation of calling it the go-to EtherNet/IP module for ControlLogix — a reliable, well-documented workhorse that integrates with a wide range of EtherNet/IP field devices, including distributed I/O, drives, and safety modules, without requiring unusual configuration gymnastics. The DLR functionality in particular draws praise: engineers who have implemented ring topologies report that the dual-port embedded switch simplifies wiring relative to using a single-port module with external ring switches, and that ring recovery after a cable fault happens quickly and transparently.

The most consistent technical complaint in community discussions involves the dual-port architecture itself — specifically, the frequent assumption that the two RJ45 ports behave as separate network interfaces assignable to different IP addresses or subnets. They do not. Both ports share a single IP address and function as an embedded switch. Engineers who do not read the architecture documentation carefully before deployment encounter confusion during commissioning, and several forum threads trace communication configuration errors directly to this misunderstanding. A second recurring issue is firmware alignment: mismatches between the 1756-EN2TR module firmware, the ControlLogix CPU firmware, and the Studio 5000 project version produce fault conditions that can be difficult to diagnose until firmware revision is identified as the root cause. Users consistently recommend aligning all firmware versions before downloading a project to a new or replaced module. A third performance-related concern appears in threads from engineers who have loaded a single 1756-EN2TR with a very large number of EtherNet/IP devices or set aggressive requested packet intervals — the module can become a connection bottleneck under these conditions, generating communication alarms that look like network hardware failures but are actually load-management issues.

On the ordering side, community members flag three mistakes with enough frequency to merit explicit attention. The first is purchasing a 1756-EN2T — the single-port variant — when the network design or plant standard calls for dual-port DLR capability, resulting in last-minute changes or rework once the module arrives on site. The second is ordering the standard 1756-EN2TR for an environment that genuinely requires conformal coating, then discovering this after the module has been installed in a corrosive atmosphere. The third is confusing the 1756-EN2TR with the older 1756-ENBT during retrofit planning, and assuming a direct like-for-like swap when the configuration, topology capabilities, and connection counts differ meaningfully between the two. All three of these mistakes are avoidable with a careful BOM review before the purchase order is submitted.

Wiring and Installation Overview

The following points cover the key requirements for physical installation and Ethernet wiring of the 1756-EN2TR. For complete installation procedures, refer to the Rockwell Automation installation instructions and ControlLogix system user manual.

  • Verify chassis slot availability and confirm the ControlLogix chassis backplane can accommodate the 1756-EN2TR's power draw before inserting the module; check controller firmware compatibility before powering up.
  • Follow plant lockout/tagout procedures if the chassis must be de-energized for installation; confirm whether your specific chassis and safety rules permit hot-insertion before proceeding with power applied.
  • Use industrial-rated shielded twisted-pair Ethernet cable suitable for 10/100 Mbps and the plant environment; observe minimum bend radius and avoid routing Ethernet alongside high-noise power conductors without proper separation.
  • For DLR topology, connect one RJ45 port to the upstream ring neighbor and the other to the downstream ring neighbor, completing the ring path; for linear daisy-chain, connect one port upstream to the network and the second port downstream to the next device in the chain — remember both ports share a single IP address.
  • After installation, verify the module OK LED transitions to a healthy state, confirm LINK LEDs are active on connected ports, and check ring status in Studio 5000 or RSLogix 5000 before adding EtherNet/IP devices to the configuration.

Initial IP Configuration and Adding the 1756-EN2TR in Studio 5000

  • Assign an IP address to the 1756-EN2TR using the BOOTP/DHCP utility or through Studio 5000 / RSLogix 5000 as supported by your firmware version; document the assigned address before proceeding.
  • In the Studio 5000 project, add the 1756-EN2TR to the I/O tree with the correct catalog number, series, firmware revision, chassis slot, and IP address — mismatch on any of these fields will prevent successful connection establishment.
  • Configure the requested packet interval (RPI) for each attached EtherNet/IP device to balance responsiveness against network load; overly aggressive RPIs across many devices are a common source of connection overloads on a single module.
  • If using DLR, verify the ring configuration in the network configuration tool and confirm that all ring nodes are healthy before going online; check the module's DLR status tags in the controller to confirm ring integrity.
  • Save and document the IP addressing scheme, firmware revision, and topology configuration for maintenance records and future expansion planning.

Wrong-Part Prevention Checklist Before You Order

Review every item on this checklist before submitting a purchase order for the Allen-Bradley 1756-EN2TR. These checks prevent the most common and costly ordering errors on ControlLogix communication module projects:

  1. Confirm the PLC platform is ControlLogix 1756 and the chassis backplane and controller firmware support the 1756-EN2TR series and revision you plan to use.
  2. Verify you truly need dual Ethernet ports with DLR capability (1756-EN2TR) rather than a single-port 1756-EN2T or a different communication module.
  3. Check that copper RJ45 10/100 Mbps is acceptable (no fiber or gigabit requirement) and that EtherNet/IP is the plant-standard protocol.
  4. Confirm environmental and coating requirements (standard vs conformal coated 1756-EN2TRK) and any temperature or contamination constraints.
  5. Validate that the expected number of TCP/IP and EtherNet/IP connections, including motion axes, fits within the 1756-EN2TR's supported limits.
  6. Make sure firmware revision for the 1756-EN2TR is compatible with your controller, I/O, and engineering software, especially in mixed-firmware plants.
  7. Check mechanical slot availability and power budget in the target ControlLogix chassis.
  8. Verify part number formatting carefully on the purchase order (1756-EN2TR vs 1756-EN2T vs 1756-EN2TRK) to avoid ordering the wrong variant.

If any item on this checklist raises a question before you order, contact LeadTime.ca for specialist confirmation — our team can verify compatibility, check real-time stock, and flag alternative variants when needed. Ships worldwide.

Frequently Asked Questions

Can the two Ethernet ports on a 1756-EN2TR be placed on different subnets or assigned separate IP addresses?

No. Both RJ45 ports on the Allen-Bradley 1756-EN2TR share a single IP address and operate as an embedded switch — they are not independent network interfaces. Traffic entering either port is available to the module under the same IP address. This is the single most common architectural misunderstanding with this module. If you need the controller to communicate on two separate subnets simultaneously, you would need two modules or a different network architecture.

How many EtherNet/IP devices can I connect through a single 1756-EN2TR without overloading it?

The 1756-EN2TR supports up to 128 TCP/IP connections according to the manufacturer datasheet. Practical load depends heavily on the requested packet intervals configured for each device — aggressive RPIs across a large number of connections are a common cause of communication alarms that appear to be hardware faults but are actually connection budget or bandwidth issues. Size your device count and RPI settings together, not separately, and verify against the module's connection limits for your specific firmware revision.

Do I actually need a 1756-EN2TR for Device Level Ring, or can I build a DLR ring using external switches and a single-port 1756-EN2T?

DLR at the supervisor level requires a module with DLR ring supervisor capability, which the 1756-EN2TR provides natively through its dual-port embedded switch. While some DLR architectures use external managed switches with ring supervisor capability, the 1756-EN2TR eliminates the need for those external components when connected directly into the ring. A 1756-EN2T is a single-port module with no embedded DLR ring supervisor function — it cannot directly terminate both ends of a DLR ring.

What is the correct approach to firmware compatibility between the 1756-EN2TR and my ControlLogix CPU?

Firmware on the 1756-EN2TR, the ControlLogix CPU, and the Studio 5000 / RSLogix 5000 project version must be aligned. Mismatches — particularly when a new or replacement 1756-EN2TR ships with a different firmware revision than the installed base — are a documented cause of configuration faults and communication errors. Always check the Rockwell Automation firmware compatibility matrix for your specific CPU series and Studio 5000 version before installing a module or downloading a project. A specialist distributor can help verify firmware series on stock units before shipment.

Is the 1756-EN2TR a direct replacement for a 1756-ENBT in an existing chassis?

The 1756-EN2TR physically fits the same ControlLogix 1756 chassis slot as the 1756-ENBT and connects to the same backplane, but it is not a configuration-identical drop-in swap. The 1756-EN2TR provides DLR capability, dual ports, and higher connection capacity that the legacy 1756-ENBT does not have — which means the I/O tree configuration, IP addressing, and potentially the network topology must be reviewed and updated as part of the upgrade. Engineers who treat it as a transparent swap without reviewing the project configuration have encountered compatibility and communication issues at commissioning.

What do the LED indicators on the 1756-EN2TR mean during normal operation and fault conditions?

The 1756-EN2TR includes status LEDs for module health and network and link status — typically labeled to indicate OK state, network activity, and link status for each port. A steady green OK LED indicates the module is operating normally. A flashing or red OK LED indicates a module fault that requires investigation in Studio 5000 diagnostics or controller tags. LINK LEDs for each port indicate whether a physical Ethernet connection is established on that port. Detailed LED state definitions are documented in the Rockwell Automation installation instructions for the 1756-EN2TR — refer to manufacturer documentation for the complete fault code and LED behavior table for your firmware revision.

Why Order the 1756-EN2TR Through LeadTime.ca

  • LeadTime.ca specializes in ControlLogix communication modules and can verify firmware series, chassis compatibility, and variant selection before your order ships — reducing commissioning risk on communication-critical hardware.
  • Real-time stock checks across multiple sourcing channels mean you get accurate availability answers, not estimated lead times based on stale catalogue data.
  • Volume and project pricing is available on request — contact the team with your BOM for a consolidated quote on ControlLogix communication modules and related hardware.
  • LeadTime.ca ships worldwide, including to customers in North America, Europe, Asia-Pacific, and beyond — wherever your project is located.

At-a-Glance Summary

  • Catalog number: Allen-Bradley 1756-EN2TR — ControlLogix Ethernet Dual-Port 10/100M Interface Module.
  • Two RJ45 copper Ethernet ports at 10/100 Mbps; both ports share one IP address via an embedded switch — not separate subnets.
  • Supports Device Level Ring (DLR) topology for ring resiliency and linear daisy-chain topologies.
  • USB 1.1 device port included for direct programming access independent of the Ethernet network.
  • Up to 128 TCP/IP connections and up to 8 motion axes over EtherNet/IP per manufacturer datasheet.
  • Maximum operating temperature: 60 °C; standard variant is 1756-EN2TR, conformal-coated variant is 1756-EN2TRK.
  • Platform: ControlLogix 1756 chassis, backplane-powered, single slot.
  • Key ordering mistake to avoid: confusing 1756-EN2TR (dual-port DLR) with 1756-EN2T (single-port, no DLR) or 1756-EN2TRK (conformal coated).
  • Pricing context: market-typical for a premium ControlLogix communication module — verify current pricing and availability on the product page.
  • Ships worldwide through LeadTime.ca — check current availability here.

You may also be interested in: