Industrial Protocols
EtherNet/IP Explained for Plant Professionals
EtherNet/IP is the industrial Ethernet protocol of choice for Allen-Bradley/Rockwell systems. Understanding how it works helps you design reliable networks and troubleshoot connectivity issues.
What is EtherNet/IP?
EtherNet/IP (Ethernet Industrial Protocol) is an industrial network protocol that adapts the Common Industrial Protocol (CIP) for standard Ethernet. Developed by Rockwell Automation and now managed by ODVA, it allows PLCs, drives, HMIs, and I/O modules to communicate over the same Ethernet infrastructure used for business networks.
How EtherNet/IP Works
EtherNet/IP uses two communication methods. Explicit messaging handles configuration, diagnostics, and non-time-critical data using TCP/IP. Implicit messaging (I/O messaging) handles real-time control data using UDP/IP multicast for speed. This dual approach provides both reliability for configuration and determinism for control.
CIP: The Common Industrial Protocol
CIP is the application layer protocol that rides on top of EtherNet/IP. It provides an object-oriented framework where every device has standard objects for identity, connection management, and device-specific functions. This standardization means a ControlLogix PLC can communicate with a Yaskawa drive or Keyence sensor using the same protocol conventions.
Network Design Considerations
EtherNet/IP works on standard Ethernet hardware but requires proper network design for reliable operation. Use managed switches with IGMP snooping for multicast traffic. Segment control networks from business networks using VLANs. Plan IP addressing schemes carefully — every device needs a unique address. Consider ring topologies (DLR) for redundancy in critical applications.
EtherNet/IP Quick Facts
| Aspect | Details |
|---|---|
| Developer | ODVA (managed by Rockwell Automation) |
| Physical Layer | Standard Ethernet (IEEE 802.3) |
| Application Layer | CIP (Common Industrial Protocol) |
| Ports Used | TCP/44818, UDP/2222 |
| Topology | Star, linear, ring (DLR) |
| Typical Cycle Time | 1-10ms for I/O data |
Key Takeaways
EtherNet/IP is the standard choice for Rockwell/Allen-Bradley systems
It runs on standard Ethernet hardware but requires industrial-rated switches for reliability
Use managed switches with proper VLAN segmentation for control networks
CIP interoperability means multi-vendor systems work together seamlessly
Device Level Ring (DLR) provides network redundancy for critical applications
Planning an EtherNet/IP network?
We design and implement EtherNet/IP networks for reliable plant communication.