Allen-Bradley EtherNet/IP: Integrating Your PLC with an IoT Gateway

Connecting an Allen-Bradley PLC to the cloud seems daunting, but it doesn't have to be. The key challenge with EtherNet/IP is that it's "tag-based," not register-based like Modbus. This guide explains how a modern industrial IoT gateway with a native EtherNet/IP driver can directly read your PLC tags (from ControlLogix or CompactLogix) and translate them to MQTT—no complex middleware like RSLinx or Kepware required. We'll show you how this IoT Gateway approach simplifies PLC data collection and reduces costs.

If your factory runs on Rockwell Automation, you know the ecosystem: Allen-Bradley PLCs (like ControlLogix and CompactLogix) are powerful, reliable, and the backbone of your operation. You also know they can feel like a "walled garden."

Getting data out of them isn't as simple as polling a Modbus register. They speak EtherNet/IP (the Common Industrial Protocol, or CIP), a sophisticated, tag-based language. This is where many PLC data collection projects hit a wall, get overly complex, or become incredibly expensive.

As an engineer, I've seen teams spend a small fortune on OPC servers and complex middleware just to get a single data point to the cloud. It doesn't have to be that hard. The secret is to stop thinking of this as a PC software problem and start thinking of it as a hardware solution. The modern industrial IoT gateway is the key.

In our guide to Modbus and the IoT Gateway, we talked about polling registers (e.g., 40001). This is simple. You just need a "memory map."

Allen-Bradley PLCs don't work that way. They use Tags.

• Modbus (Register-Based):Value = Read(Device 5, Register 40001)
• EtherNet/IP (Tag-Based):Value = Read(Device 'PLC_Line_1', Tag 'Motor_Speed_RPM')

This is far more intuitive and powerful, but it means your data collector can't just be a simple "Modbus poller." It needs to be an IoT Gateway that is smart enough to browse the PLC's tag list and request data by name. This is a fundamentally more advanced task, and it's why many cheap converters or basic gateways fail.

A true IoT Gateway built for Allen-Bradley PLCs isn't just a protocol converter; it's a native speaker. It contains the EtherNet/IP (CIP) driver needed to communicate directly with your ControlLogix or CompactLogix controller.

This IoT Gateway simplifies the entire process into three steps:

1. Connect: The IoT Gateway connects to the PLC's Ethernet port (just like another HMI or programming laptop).
2. Request: The IoT Gateway sends a request: "Hello, 192.168.1.10. Please give me the current value of the tag named 'Motor_Speed_RPM'."
3. Translate: The PLC responds with the value (e.g., 1750.5). The IoT Gateway then takes this data, wraps it in a clean JSON format with a timestamp, and publishes it to the cloud via MQTT.

Your cloud platform never needs to know what EtherNet/IP or "CIP" is. It just receives: {"timestamp": "2025-11-04T11:30:00Z", "tag": "Motor_Speed_RPM", "value": 1750.5}

This makes the IoT Gateway the perfect, hassle-free bridge.

This isn't theory. Here's the "code-free" process on a Robustel IoT Gateway (like the EG5120) using our Edge2Cloud Pro software:

• Step 1: Prep the PLC? (Barely). Unlike Siemens PLCs, which require configuration changes in TIA Portal, Allen-Bradley PLCs often just work. You just need to know the IP address of the PLC and the exact names of the tags you want to read. (Note: Tags must be set as "External Access: Read" or "Read/Write" in Studio 5000).
• Step 2: Configure the IoT Gateway
  • In the gateway's web GUI, go to Edge2Cloud Pro.
  • Add Device: Name: Line_1_PLC, Protocol: Allen-Bradley EtherNet/IP
  • IP Address: 192.168.1.10 (Your PLC's IP)
  • Add Tag: Name: Motor_Speed_RPM, Address: Motor_Speed_RPM (The tag name is the address!)
  • Add Tag: Name: Fault_Code, Address: Machine_Fault_Code
• Step 3: Configure Cloud
  • Go to the "Cloud" tab, enter your MQTT broker details.
• Click Save & Run.

That's it. Your Allen-Bradley PLC is now connected to the cloud. This simple, elegant workflow is the power of a modern IoT Gateway.

For years, the "official" way to do this was to buy a powerful PC, install a Windows Server OS, and buy an expensive middleware license from vendors like Kepware (KepServerEX) or even Rockwell itself (RSLinx). This server would sit on the factory floor, talk to the PLCs, and then (maybe) talk to the cloud.

A modern IoT Gateway makes this entire stack obsolete.

This is the biggest win. That PC and software stack can cost $5,000 - $15,000 in licensing and hardware before you've collected a single data point. An industrial IoT gateway is a single, solid-state piece of hardware that costs a fraction of that. The EtherNet/IP driver is included. It's a massive TCO reduction.

That middleware server relies on the factory's internal IT network. What if the IT network goes down? What if it's insecure or blocks your ports? A cellular IoT Gateway (using 4G or 5G) bypasses the internal network entirely. It creates its own secure, private "data pipe" directly to the cloud, isolating your critical Allen-Bradley PLC from the enterprise network.

This is the killer app for SIs and machine builders. An IoT Gateway combined with a management platform (like Add One Product: RCMS ) doesn't just pull data out—it lets you in. Securely. An engineer in another country can launch Rockwell's Studio 5000 software, connect to the IoT Gateway's secure VPN, and get remote access to the CompactLogix or ControlLogix PLC to troubleshoot, patch, or upload new logic. This is the value of a true IoT Gateway platform.

Stop thinking Allen-Bradley data is "locked up" or requires a massive, expensive software project. It's not. The EtherNet/IP protocol is powerful, and with the right tool, it's easy to access.

A modern industrial IoT gateway is that tool. It's a single, rugged device that securely reads EtherNet/IP tags natively, translates them to MQTT for the cloud, and can even provide secure remote access for your engineers—all without a single PC or middleware license. This IoT Gateway solution is simpler, cheaper, more secure, and more reliable.