TL;DR
EtherNet/IP communication errors on a CompactLogix 5380 start with physical layer checks: cable, switch port, and IP address. Then check the Studio 5000 connection configuration for timeout and RPI settings.
What you might see
- communication fault LED on the controller or remote I/O adapter
- Studio 5000 shows 'connection error' or 'target not found' on a remote module
- process controller logs connection timeout faults
- EtherNet/IP status indicator solid red or flashing red
Likely causes
Faulty or disconnected Ethernet cable at the controller, remote adapter, or switch port
Managed switch port configuration mismatch (duplex, VLAN, or QoS setting)
IP address conflict between the controller and another device on the subnet
RPI (requested packet interval) set too fast for the network switch's forwarding rate
Required tools
- Laptop with Studio 5000 Logix Designer
- Ethernet cable (known good, CAT5e or better)
- Network switch management console access (if managed switch)
Safety first
- Making network configuration changes on a live PLC controlling safety-critical or production processes requires coordination with the process operator and a change management approval.
- Changing the controller IP address while online will drop the Studio 5000 connection. Confirm the new address with the network administrator before changing.
Procedure
- 1
Check the physical Ethernet cable at the controller EtherNet/IP port and at the remote adapter. Reseat both ends. Replace the cable with a known-good cable as a quick test.
- 2
Verify the switch port activity LED is flashing. No activity means no link. Check the switch port for port-disable or VLAN misconfiguration.[1]
- 3
In Studio 5000, go to the Controller Properties, then to the Ethernet tab. Confirm the controller IP address and that the subnet mask matches the rest of the network.
- 4
Use a laptop on the same subnet to ping the controller's IP address. A successful ping but continued connection error means the EtherNet/IP connection parameters are the issue.
- 5
Check for IP address conflicts by pinging both the controller IP and the remote adapter IP from the laptop. Both should respond uniquely.[1]
- 6
In Studio 5000, right-click the remote adapter in the I/O tree and select properties. Reduce the RPI to no faster than 10 ms on a standard managed switch if you are seeing intermittent timeouts.[1]
- 7
Check the controller's Ethernet diagnostic page in Studio 5000 for CRC error counts or input queue overflows, which indicate network congestion or a bad cable.
Sources
Allen-Bradley CompactLogix 5380 Controllers User Manual (Pub 5069-UM001), Rockwell Automation (Allen-Bradley)
Allen-Bradley CompactLogix 5380 Controllers User Manual, EtherNet/IP configuration and diagnostics (general)
View source
More guides for Allen-Bradley (Rockwell) CompactLogix 5380
How to replace the backup battery on an AB CompactLogix 5380 PLC
The CompactLogix 5380 battery alarm is straightforward: order the correct lithium battery, replace it with the controller powered on to preserve memory, and acknowledge the alarm. The battery typically lasts 5 to 7 years.
How to replace a failed I/O module on an AB CompactLogix 5380 PLC
A failed I/O module shows a red fault LED and logs a fault code in Studio 5000. Note the slot number and module catalog number, go online with the PLC, inhibit the module, swap it, and re-enable it without modifying the program.
How to recover from program corruption on an AB CompactLogix 5380
Program corruption shows as a major fault on power-up or a checksum error in the fault log. Restore from the latest validated ACD backup in Studio 5000 or from the SD card if auto-restore was configured.
How to diagnose sensor reading drift on an AB CompactLogix 5380 analog input
Analog input drift is usually wiring noise or a loose field terminal. Measure the sensor signal directly at the field terminal and compare to the PLC tag value. If they differ, the I/O module or scaling is the issue. If the signal itself is noisy, fix the cable shielding.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.