US What EtherNet/IP is
EtherNet/IP (Ethernet Industrial Protocol) is an industrial network protocol that carries the Common Industrial Protocol (CIP) over standard Ethernet and TCP/IP. It connects PLCs, remote I/O, drives, robots, HMIs and safety devices on a plant network, and it is one of the most widely used industrial Ethernet protocols, especially in North America.
The “IP” stands for Industrial Protocol, not Internet Protocol, which is the most common confusion. EtherNet/IP does use the Internet Protocol underneath, but the name refers to the CIP application layer that sits on top. It was introduced in 2001, is managed by ODVA, and is standardized in IEC 61158 and IEC 61784-1 as Communication Profile Family 2.
Because it uses unmodified Ethernet, EtherNet/IP runs on standard cabling, standard network interfaces and managed industrial switches, and it can share a network with ordinary IT traffic when the network is designed for it.
How EtherNet/IP works
CIP organises every device as a set of objects, such as identity, assembly and connection objects, which makes devices from different makers look alike to the controller. Each device ships with an Electronic Data Sheet (EDS) file that tells the engineering software what it can do. EtherNet/IP moves CIP messages in two ways.
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Explicit messaging. Request and response over TCP port 44818, used for configuration, diagnostics, reading parameters and other non-time-critical data.
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Implicit (I/O) messaging. Cyclic I/O data sent over UDP port 2222 using a producer-consumer model. The controller sets a requested packet interval (RPI) for each connection, typically from a few milliseconds upwards, and data can be unicast or multicast.
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Scanners and adapters. A scanner, usually the PLC, opens connections and owns the outputs. An adapter, such as a remote I/O station or drive, answers with its inputs. In CIP terms they are the originator and the target.
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CIP extensions. CIP Safety adds functional safety over the same network, CIP Sync and CIP Motion use IEEE 1588 Precision Time Protocol for coordinated motion, and CIP Security adds TLS-based authentication and encryption.
EtherNet/IP compared with other industrial Ethernet protocols
The choice of protocol usually follows the controller vendor and the plant standard rather than raw performance. The table compares the four most common options.
| EtherNet/IP | PROFINET | Modbus TCP | EtherCAT | |
|---|---|---|---|---|
| Managed by | ODVA | PI (PROFIBUS and PROFINET International) | Modbus Organization | EtherCAT Technology Group |
| Application layer | CIP | PROFINET IO | Modbus | CANopen and other profiles over EtherCAT |
| Transport | TCP and UDP over IP | Ethernet frames for real-time; UDP for set-up | TCP, port 502 | Ethernet frames processed on the fly |
| Standard switches | Yes | Yes, except IRT | Yes | No, devices form the line |
| Typical cycle | Around 1–100 ms | Around 1–10 ms; IRT below 1 ms | Polled, tens of ms | Often below 100 µs |
| Commonly found with | Rockwell Automation and many North American plants | Siemens and many European plants | Meters, gateways and PC-based systems | Motion control and high-speed test |
Many plants run more than one. Gateways and multi-protocol devices translate between them, and an industrial PC can act as a client on several networks at once.
Designing a network for EtherNet/IP
EtherNet/IP works on ordinary Ethernet, but cyclic I/O traffic needs a network that is designed for it rather than left flat. The main points are well established in ODVA and vendor design guides.
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Use managed switches. Implicit I/O is often multicast, so switches need IGMP snooping and a querier to stop that traffic flooding every port.
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Segment the network. Put control traffic in its own VLAN and keep office and video traffic away from I/O connections.
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Prioritize I/O. EtherNet/IP marks its packets with DSCP values, and switches can use quality of service to forward them first.
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Plan redundancy. Device Level Ring (DLR) links devices with embedded switches into a ring topology that recovers from a cable break in a few milliseconds, and switch-level rings protect the backbone.
EtherNet/IP hardware
Several managed industrial Ethernet switches in our range list EtherNet/IP and PROFINET Conformance Class A support, together with IEEE 1588 v2 PTP, ring redundancy and extended temperature ratings. Industrial PCs and gateways join EtherNet/IP networks through software stacks or adapter cards, either as a scanner reading remote I/O or as an adapter presenting data to a PLC. A dedicated Ethernet port for the control network keeps I/O traffic apart from the plant or office LAN, and a network interface with hardware timestamping helps where CIP Sync or CIP Motion needs precise time.
Quick answers on EtherNet/IP
EtherNet/IP: common questions
What does the IP in EtherNet/IP stand for?
Industrial Protocol. It refers to the Common Industrial Protocol (CIP) carried over Ethernet, not to the Internet Protocol, even though EtherNet/IP also uses the Internet Protocol underneath.
Is EtherNet/IP TCP or UDP?
Both. Explicit messages for configuration and diagnostics use TCP port 44818. Real-time I/O uses UDP port 2222, which avoids the delays of TCP retransmission.
Is EtherNet/IP a Rockwell protocol?
It started there but is open. Rockwell Automation developed it, and it is now managed by ODVA, a vendor association. Hundreds of manufacturers make conformance-tested EtherNet/IP devices.
What is the difference between EtherNet/IP and PROFINET?
Mainly the vendor base and the transport. EtherNet/IP carries CIP over TCP and UDP and is common in North American plants. PROFINET sends real-time data directly in Ethernet frames, offers IRT for sub-millisecond cycles and is common in Europe.
What is an EDS file?
A device description. The Electronic Data Sheet is a text file from the device maker that tells the engineering software the device’s identity, connections and parameters, so it can be added to a project.
We supply managed industrial switches, industrial PCs and gateways for EtherNet/IP networks, configured as standard with the VLAN, QoS and redundancy settings your control system needs.