TECHNOLOGY OVERVIEW SERIES

PUB00138R81

FEBRUARY 2024

EtherNet/IP –CIP on Ethernet Technology
TM

EtherNet/IP™ was introduced in 2001 and today is the mostdeveloped, proven and complete industrial Ethernet network
solution available for manufacturing and process automation. EtherNet/IP is a member of a family of networks that
implements the Common Industrial Protocol (CIP™) at its
upper layers. CIP encompasses a comprehensive suite ofmessages and services for a variety of manufacturing andprocess automation applications, including control, safety,
security, energy, synchronization, motion, configuration andinformation. As a truly media-independent protocol that is
supported by hundreds of vendors around the world, CIP
provides users with a unified communication architecture
throughout the manufacturing enterprise.
With media independence comes the ability to choose
the CIP Network best suited for each application. One ofthese possible choices is EtherNet/IP, which adapts CIP to
Ethernet technology. Why adapt CIP to Ethernet?
Ethernet, and TCP/IP– the Ethernet standard – is the same
network technology used in the majority of local area network (LAN) and wide area network (WAN) architectures
found in commercial applications around the world. Thesearchitectures connect computers and peripherals to one
another, link business operations to the enterprise, provide
users with access to web-based applications and encompass an installed base numbering in the billions of nodes. Byleveraging the economies of scale in this proven commercial technology, EtherNet/IP provides users with the tools
to deploy standard Ethernet technology for manufacturing
and process applications, improving connectivity between
people, partners and processes, devices, departments andsystems in industrial applications, and opens up new opportunities for productivity, efficiency and flexibility.
EtherNet/IP offers several unique advantages for manufacturing
and process automation applications:

2

•


Completeproducer-consumer services let you
simultaneously and seamlessly control, configure
and collect data from intelligent devices over a single
network or use a single network as a backbone formultiple distributed CIP Networks.

•

 ompatible with standard Internet protocols —Ce.g., HTTP, FTP, SNMP, and DHCP — and standard
industrial protocols for data access and exchangesuch as OPC UA.

• ompliance with IEEE Ethernet standards provides
Cusers with a choice of network interface speeds— e.g., 10, 100 Mbps, 1 Gbps and beyond — anda flexible network architecture compatible withcommercially available Ethernet installation options
including copper, fiber, fiber ring and wireless,and topologies including star, linear and ring.

•Compatible with the Ethernet-APL physical layerthat enables long reach and hazardous area capable
Ethernet for process field devices. Ethernet-APL is
made up of the IEEE 802.3cg-2019 (10BASE-T1L),
IEC 60079, and IEC 61158 standards.

•

Parallel Redundancy Protocol (PRP) support, as
defined in international standard IEC 62439-3, which
provides high-availability for Ethernet networks.
PRP technology creates seamless redundancy
by sending duplicate frames to two independent
network infrastructures.

•

Options for industrially rated devices incorporating
IP67-rated connectors (RJ45 or M12) with moduleand network status LEDs with device labeling forease of use•W
ith the optional QuickConnect™ feature,minimization of power-up delays for applications
where devices must connect and be ready tocommunicate with minimal delay (e.g., end of arm
robotic tool changers)•

upport for functional safety with CIP Safety™
S
implemented in devices•

ynchronization of clocks across a system ofSinterconnected devices using CIP Sync™

•

 upport of high-speed motion control applications
S
with CIP Motion™

•

Device level security with CIP SecurityTM•

Energy usage monitoring and management via
CIP EnergyTM

What is EtherNet/IP?
CIP Motion™
ProfilesMotor Control
ProfilesCIP Security™
Objects

CIP Sync™
Objects

CIP Energy™
Objects

Transducer
ProfilesI/O
ProfilesOther
ProfilesSemiconductor
ProfilesSafetyObject Library

Object Library(Communications, Applications, Time Synchronization)

Data Management Services
Explicit and I/O Messages

CIP Security™
Objects(TLS, DTLS)

Translation Services for HART®, IO-Link®,
and Modbus® Device Integration

CIP Safety™
ProfilesSafety Services
and Messages

Connecting Management, Routing

CompoNet
Network and Transport

ControlNet
Network and Transport

DeviceNet
Network and Transport

Ethernet
CSMA/CD

CompoNet
Time Slot

ControlNet
CTDMA

CAN
CSMA/NBA

Ethernet
Physical Layer

CompoNet
Physical Layer

ControlNet
Physical Layer

DeviceNet
Physical Layer

Internet Protocol

Network Adaptations of CIP

TCP/UDP

Common Industrial Protocol (CIP™)

CIP Security™
ProfilesFigure 1: EtherNet/IP as Part of the CIP OSI Model

EtherNet/IP, like other CIP Networks, follows the Open Systems
Interconnection (OSI) model, which defines a framework for
implementing network protocols in seven layers: physical, datalink, network, transport, session, presentation and application.
Networks that follow this model define a complete suite of
network functionality from the physical implementation throughthe application or user interface layer. As with all CIP Networks,
EtherNet/IP implements CIP at the Session layer and above
and adapts CIP to the specific EtherNet/IP technology at theTransport layer and below. This network architecture is shownin Figure 1.
Ethernet has the unique characteristic of being a networkwith an active infrastructure. Therefore, unlike typicalindustrial networks - which generally have a passive
infrastructure that limits the number of devices that can beconnected and the way they can be connected - theEtherNet/IP network infrastructure can accommodate avirtually unlimited number of point-to-point nodes, and withembedded switch technology, can also support linear andring topologies providing users with unsurpassed flexibility
in designing networks that accommodate their current
requirements while enabling easy, cost-effective expansion
in the future.
To further decrease complexity, EtherNet/IP provides a single
point of connection for both configuration and control
because EtherNet/IP supports both I/O (or implicit) messages:
those that typically contain time-critical control data andexplicit messages, and those in which the data field carries
protocol information typical of client/server transactions usedin configuration and data collection. As a producer-consumer
network that supports multiple communication hierarchies

TECHNOLOGY OVERVIEW SERIES: ETHERNET/IP
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and message prioritization, EtherNet/IP provides more
efficient use of bandwidth than other device networks thatuse a strictly source-destination model. EtherNet/IP systems
can be configured to operate either in a controller/device typeof relationship or in a distributed control architecture using
peer-to-peer communications.

The Physical Layer
EtherNet/IP uses standard IEEE 802.3 technology at the
Physical and Data Link Layers. This standard provides a
specification for physical media, defines a common frame
format for moving packets of data between devices andsupplies a set of rules for determining how network devices
respond when two devices attempt to use a data channel
simultaneously. This is known as CSMA/CD (Carrier Sense
Multiple Access/Collision Detection).
As a network with an active infrastructure, EtherNet/IP is
typically configured using a series of network segments
constructed of point-to-point connections in a starconfiguration. The core of this network topology is aninterconnection of Ethernet Layer 2 and Layer 3 switches that,as previously mentioned, can accommodate an unlimited
number of point-to-point nodes. However, EtherNet/IP
networks can also implement linear branching and singlefault tolerant ring topologies by utilizing embedded switch
technology and Device Level Ring (DLR™) technology.
These alternate topologies can be combined to optimize
cable routing and machine communications layout. Most
manufacturers offer pre-made or custom “patch” cables ina wide variety of lengths. Typically, a backbone of switches,in which each switch isolates a machine or a major partof a machine, are connected with high-speed copper orfiber optic cables. The other ports of the switch can beconnected using twisted pair (e.g., CAT 5E, CAT 6) or fiber
cables to the control devices for that part of the machine or
manufacturing process. At a higher level, enterprise networks
built on EtherNet/IP networks can make use of commercial
technology to create architectures that range from complete
separation to a fully converged plant-wide Ethernet.
Depending on their performance requirements, users can
specify either Industrial EtherNet/IP products that have
implemented options for the physical layer to improvereliability in industrial applications - such as high-noise
applications or harsh environments with liquid and dust
exposure requiring IP67 ratings - or Commercial Off-theShelf (COTS) products. In addition, CAT 5E or later Ethernet
cable is recommended for reliability in manufacturing
applications, as this cable provides greater noise immunityand other safeguards against harsh industrial environments.
Both copper (shielded or unshielded twisted pair) and fiber
cabling options are available, as well as sealed or non-3

sealed RJ45 connectors for copper wires and LT, SC, ST or
MTRJ connectors for fiber optic cables.

The Data Link Layer
IEEE’s 802.3 specification is also the standard used fortransmitting packets of data from device to device on the
EtherNet/IP Data Link Layer. Ethernet employs a CSMA/CD
media access mechanism that determines how networked
devices share a common bus (i.e., cable), and how they detect and respond to data collisions.
Originally, Ethernet worked in a half-duplex mode ofoperation, meaning that a node could send or receive data,
but it could not do both at the same time. This caused data
traffic jams, which are unacceptable in time-critical control
applications. Now, with full-duplex Ethernet (the de facto
standard today), networked devices can both send andreceive packets of Ethernet data at the same time. This,
along with advancements in switching technology makes
Ethernet suitable for use in the breadth of manufacturing orprocess applications.

The Network andTransport Layers
At the Network and Transport Layers, EtherNet/IP utilizes
standard TCP/IP (Transmission Control Protocol/Internet
Protocol) to send messages between one or more devices.
TCP/IP has been used in office applications for decades, andhas wide familiarity and support. It provides the necessarycommunication protocol features needed to implement
fully functional networks (i.e., an addressing scheme andmechanisms for establishing a connection with a device andexchanging data).

Application

FTP

HTTP

Transport

CIP

TCP

OSPF

Network

OPC

IGRP

ARP

SNMP

BOOTP
DHCP

UDP

Explicit
Messaging

ICMP

Real-TimeVO Control

IGMP
RARP

IP

Data Link
PhysicalIEEE 802.3 Ethernet

Figure 3: CIP – fully compatible with widely used
Ethernet and Internet protocols

The Media Access Control (MAC) protocol of the IEEE 802.3
specification is what actually allows devices to “talk” on the
Ethernet network. Each device has a unique MAC addresscomprised of a 6-byte number that is regulated by IEEE andthe product manufacturer to maintain uniqueness. This MAC
address is used in the source address (SA) field of the frame
to indicate what node sent the frame, and it is used in thedestination address (DA) field to indicate the destination of
the frame. Setting the first bit to a “1” in the DA field indicatesa packet of data for multiple destinations, and enables an
Ethernet node to transmit a single data packet to one or more
destination nodes.
A single frame of industrial EtherNet/IP can contain up to 1,500
bytes of data, depending on the application requirements. The
combination of real-time control with high-data capacity has
made industrial Ethernet the network technology of choice,as more intelligence is embedded into smaller and lessexpensive devices. By utilizing standard Ethernet along withstandard TCP/IP and UDP, EtherNet/IP is uniquely positioned
to provide ease of configuration and operation, high data
throughput, straightforward connectivity and provides theability to merge the factory floor with the enterprise.

4

Also, at these layers, the standard CIP messages used by all
CIP Networks are encapsulated. This TCP/IP encapsulation
allows a node on the network to embed a CIP message
inside an Ethernet message and send it to another node on
the network, using the standard TCP/IP protocol.
By using standard TCP/IP and Ethernet, the lower layers of
the TCP/IP stack and Ethernet interface chips (e.g., MAC
controllers) will pass these messages through standard
Ethernet infrastructure (e.g., managed or unmanaged
switches, routers, etc.) to the destination node. TCP/
IP is used in EtherNet/IP to send CIP explicit messages,
which are used to perform client-server type transactions
between nodes. Some of these transactions will establish
communications relationships that leverage UDP/IP, toexchange real-time data with other nodes on the factory
floor. This is all seamless from the application perspective,
which is made possible by utilizing standard Ethernet, TCP/
IP and UDP/IP communications.

The TCP/IP Suite consists of the following:••

The TCP portion of the TCP/IP protocol is aconnection-oriented,
point-to-point(unicast)transport mechanism that provides data flow
control, fragmentation reassembly and message
acknowledgements. Nodes will receive eachmessage and acknowledge to the sender that it
was received. If the message is fragmented acrossmultiple frames, the sender will send the next
fragment, which is acknowledged. This repeats
until the entire message is received. At that time
the receiving node will process the data and act
accordingly. Since TCP is ideal for the reliabletransmission of large and small quantities of data,
EtherNet/IP uses TCP/IP to encapsulate CIP explicit
messages, which are generally used to transmit
configuration and diagnostic data, and also used toestablish real-time (implicit) data transfers between
devices.
The IP portion of the TCP/IP protocol is themechanism that assures packet routing throughmultiple possible paths. The ability to send
messages to their destinations even when the
primary path is disrupted is the basis of the Internet
Protocol. Because EtherNet/IP uses standard IP,
this same type of routing is used to maintain proper
separation of factory floor control elements andother manufacturing systems through the use ofstandard infrastructure such as managed switchesand Layer 3 routers.

For real-time data transfer, EtherNet/IP also employs UDPover IP to transport I/O messages that contain time-criticalcontrol data. UDP is a connectionless transfer mechanismthat has low protocol overhead yielding smaller packet
sizes and makes multicasting data to more than one
destination possible. The smaller packets and multicastingsupport make the Producer/Consumer model possible
with EtherNet/IP, and provide for streamlined data flow
through the system, while the CIP Connection mechanism
provides timeout mechanisms that can detect data delivery
problems. For these reasons, UDP is well-suited to the taskof transferring real-time implicit (i.e., I/O) data on EtherNet/IP.
EtherNet/IP uses two forms of messaging:• U nconnected messaging is used in the connection
establishment process and for infrequent, low-priority
explicit messages. The unconnected resources in a device
are referred to as the Unconnected Message Manager, or
UCMM. Unconnected messages on EtherNet/IP utilize
TCP/IP resources to move messages across Ethernet.
• C onnected messaging on EtherNet/IP utilizes
resources within each node that are dedicated inadvance to a particular purpose, such as frequent explicit
message transactions or real-time I/O data transfers.
Connection resources are reserved and configured using
communications services available via the UCMM.

TECHNOLOGY OVERVIEW SERIES: ETHERNET/IP
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The process of opening a connection is called Connection
Origination, and the node that initiates the connection
establishment request is called a Connection Originator,
or just an Originator. Conversely, the node that responds
to the establishment request is called a Connection Target,
or a Target.
EtherNet/IP has two types of messaging connections:• E xplicit messaging connections are point-to-point
relationships that are established to facilitate requestresponse transactions between two nodes. These
connections are general purpose in nature and are
typically used for frequent requests between thetwo nodes. They can be used to reach any networkaccessible items within a device. Explicit messaging
connections utilize TCP/IP services to move messages
across Ethernet.
• Implicit (I/O data) connections are established tomove application-specific I/O data at regular intervals.
These connections can be set up as one-to-one
relationships or as one-to-many in order to take fulladvantage of the producer-consumer multicast model.
Implicit messaging uses UDP/IP resources to makemulticast data transfers over Ethernet a reality.

EtherNet/IP supports three device classes based on network
communication capabilities: Messaging Class, Adapter
Class and Scanner Class. Each class supports a basic setof communications services, but may provide other optional
services too.
Messaging Class products support explicit messaging(connected or unconnected) that is sent to or received
from all other classes of products. Messaging Class
products are the targets of explicit message connection
requests, and may also be originators of these requests,
but they do not send or receive real-time I/O data.
Examples of products in this class include:• D evices that perform configuration and programmingof HMI products, robots and PLCs;• D
 evices with applications that provide an operator
interface to control systems (i.e., HMI products);• S oftware applications that do not require real-time I/O
response (e.g., MIS applications); and• Network configuration and diagnostic tools.

5Adapter Class products are the targets of real-time I/O data
connection requests from Scanner Class products. They
cannot send or receive real-time I/O data unless they arerequested to do so by a scanner, and they do not store ororiginate the data communications parameters necessary
to establish the connection. Adapter Class products receive
explicit message requests (connected and/or unconnected)
from all other classes of products. They may also exchange(peer) data using explicit messages with any class of device,
but they typically cannot originate such relationships.
Examples of products in this class include:•

I/O devices such as I/O blocks or racks of I/O modules
that produce and consume real-time I/O data;• Weigh scales, welders, drives and robots that send andreceive real-time data at the request of PLCs and othercontrollers;• Weigh scales, welders, drives and robots that also

receive explicit messages from control systems suchas controllers and PLCs; and• HMI products that send or receive explicit or real-time
I/O data to/from PLCs or other controllers.

Scanner Class products are the originators of I/O data
connection requests to Adapter Class products, as wellas to other Scanner Class products that support Adapter
Class functions (i.e., peer-to-peer explicit or I/O data). These
products are typically also originators or targets of explicit
connection requests to and from other classes of products,
and they can also send or receive explicit messages to orfrom all other classes of products.
Examples of products in this class include:• P LCs, PC-based controls, other controllers and robots
that send and receive real time data to and from I/O
devices, PLCs, PC-based controls, drives, robots,weigh scales, welders and HMI products;• PLCs, controllers and robots that send and receive

explicit message data to and from other PLCs, robots,weigh scales, PC-based controls, welders and HMI
products.

The Upper Layers
EtherNet/IP uses the Common Industrial Protocol (CIP),
which is an object-oriented protocol, at the upper layers.
Each CIP object has well-defined attributes (data), services(commands) and behaviors (reactions to events). CIP’s
producer-consumer communication model provides more
efficient use of network resources than a pure source-destination model by allowing the exchange of application
information between a sending device (e.g., the producer)
and many receiving devices (e.g., the consumers) without
requiring data to be transmitted multiple times by a single

6source to each individual destination. In producer-consumer networks, a message is identified by its connection ID,
not its destination address (as is the case with source-destination networks). In EtherNet/IP this is realized using the
combination of the Connection ID and an IP Multicast groupaddress. Thus, the producer-consumer model provides aclear advantage for users of CIP Networks by making efficient use of network resources in the following ways:• If a node wants to receive data, it only needs to ask for
it once to consume the data each time it is produced.

• If a second (third, fourth, etc.) node wants the samedata, when it asks for it, the device will provide themulticast address and Connection ID of the message
already being produced, so that all nodes will
simultaneously receive a single message from the
network.
CIP also includes “device types” for which there are
Device Profiles. For a given device type, the Device
Profile will specify the set of CIP objects that must be
implemented, configuration options and I/O data formats.
This consistency in object implementation for a given
device type provides another clear advantage for usersof CIP Networks by promoting a common applicationinterface for a given device type and interoperability in
networks comprised of devices from multiple vendors. For
applications where unique functionality is required, it isalso possible for an EtherNet/IP vendor to define additional
vendor-specific objects in an EtherNet/IP-compliant productin order to support the functional requirements of particularapplications that are unique to that vendor.
Seamless bridging and routing is perhaps the mostsignificant advantage for users of CIP Networks for it is thismechanism that most protects the user’s investment for the
future. The ability to originate a message on one CIP
Network, such as EtherNet/IP, and then pass it to another
CIP Network, such as DeviceNet®, with no presentation at
the Application Layer, means that users can incorporate
incremental application improvements to existing
installations and/or integrate automation systems withdiagnostic, prognostic and/or IT applications. Seamlessbridging and routing between both homogeneous andheterogeneous CIP Networks is enabled by a set of CIP
objects that defines CIP routing mechanisms (this is not theInternet Protocol routing discussed earlier) for a device to
use when forwarding the contents of a message producedon one network port to another. This mechanism does notalter the contents of a message during the routing process.
When using this mechanism, the user’s only responsibility is
to describe the path that a given message must follow. CIP
ensures that devices that act as gateways between the
different CIP Networks handle the message correctly,
independent of the CIP Networks involved.

Management of the
EtherNet/IP Technology
EtherNet/IP is managed by ODVA, an international association of theworld’s leading automation companies. ODVA’s EtherNet/IP management
responsibilities include:• Publishing The EtherNet/IP Specification;• Overseeing the process to incorporate new enhancements to The
EtherNet/IP Specification;• Licensing the EtherNet/IP Technology to companies desiring to
make and/or sell EtherNet/IP-compliant products;• Promoting industry awareness of EtherNet/IP and its benefits; and• Helping to ensure compliance of EtherNet/IP products withthe specification through conformance testing and conformity
reporting.
For more information about EtherNet/IP, CIP or ODVA, visit ODVA at
www.odva.org.

About ODVAODVA is an international standards development and trade organization
with members from the world’s leading automation suppliers. ODVA’s
mission is to advance open, interoperable information and communication
technologies for industrial automation. Its standards include theCommon Industrial Protocol or “CIP™,” ODVA’s media independent
network protocol – and industrial communication technologies including
EtherNet/IP, DeviceNet and others. For interoperability of production
systems and their integration with other systems, ODVA embraces the
adoption of commercial-off-the-shelf, standard Internet and Ethernet
technologies as a guiding principle. This principle is exemplified by
EtherNet/IP – today’s leading industrial Ethernet network. Visit ODVA
online at www.odva.org.

ODVA
Ann Arbor, Michigan, USA
TEL: +1 734-975-8840
FAX: +1 734-922-0027
WEB: www.odva.org
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TECHNOLOGY OVERVIEW SERIES: ETHERNET/IP
PUB00138R8©2024 ODVA, Inc. All rights reserved.

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