Learn EtherNet/IP for Industrial Automation: Network Architecture Design

EtherNet/IP has become the nervous system of modern industrial plants. When you depend on UPS systems, static transfer switches, inverters, and other power protection equipment to keep production running, that nervous system cannot afford to misfire. I have seen “small” network design shortcuts turn into real plant events: nuisance UPS alarms flooding SCADA, drives dropping I/O connections, and in the worst cases, power systems failing to transfer cleanly during utility disturbances because control traffic was delayed.

In this article, I will walk through how to design EtherNet/IP network architecture specifically for industrial automation, with an eye toward protecting critical power systems. The guidance is grounded in the EtherNet/IP and CIP model as described by ODVA, in plant-wide architectures such as the Rockwell Automation–Cisco Converged Plantwide Ethernet (CPwE) approach, and in practical field experience commissioning industrial Ethernet in harsh environments.

EtherNet/IP Fundamentals for Power and Automation Engineers

EtherNet/IP (Ethernet Industrial Protocol) is an open industrial fieldbus standard that runs the Common Industrial Protocol (CIP) over standard IEEE 802.3 Ethernet and Internet Protocol. ODVA, together with Rockwell Automation and other vendors, governs the specification and certifies device interoperability. Bürkert and other automation suppliers emphasize that EtherNet/IP rides on the same Ethernet/TCP/UDP stack used in office networks, which makes it easier to integrate plant and enterprise systems without proprietary gateways.

Conceptually, EtherNet/IP aligns with the OSI model. The physical and data-link layers are standard Ethernet. IP sits at the network layer, TCP or UDP at the transport layer, and the CIP object model defines application behavior. CIP is object‑oriented: drives, I/O adapters, valves, UPSs, and gateways expose standardized objects and device profiles, which allows engineering tools and PLCs to configure and monitor them consistently. Embien describes how EtherNet/IP uses an encapsulation protocol that packages CIP messages into TCP or UDP data fields, with session information and length in a header.

There are two distinct communication styles on EtherNet/IP, and understanding them is critical when you are carrying both real‑time power control and higher‑level supervision on the same network.

Explicit messaging is ideal for engineering workstations, SCADA, and maintenance tools talking to power protection devices. Implicit messaging is where your time‑critical control lives: drive speed references, transfer switch status, protection interlocks. EtherNet/IP also supports CIPSync time synchronization compatible with IEEE 1588 Precision Time Protocol, enabling sub‑microsecond clock alignment for tight coordination, such as high‑precision motion or synchronized switching.

Because implicit I/O often runs over UDP with minimal overhead, the network itself must guarantee low jitter and minimal congestion. That is where architecture becomes just as important as protocol choice.

What Counts as a Real EtherNet/IP Control Network

ODVA and EtherNet/IP practitioners make a useful distinction between a true EtherNet/IP control network and a blended Ethernet segment that just happens to carry some EtherNet/IP packets. An EtherNet/IP control network is a portion of your Ethernet infrastructure where ODVA‑certified EtherNet/IP devices exchange CIP communications, and where the architecture has been designed specifically for real‑time control traffic.

In contrast, a blended network with many non‑EtherNet/IP devices, significant general IT traffic, and no clear segmentation is discouraged for machine control. It is common to find this pattern in older plants where someone “just dropped” a few drives and UPSs onto an existing office switch. The network works most of the time, until a backup job or camera stream coincides with a breaker status scan, and latency spikes.

For critical power systems, the EtherNet/IP control portion should be intentionally architected: its own VLANs and subnets, ODVA‑certified devices wherever possible, and clear rules about which other traffic is allowed to coexist.

Core Architectural Principles for EtherNet/IP Networks

Authors of “The Everyman’s Guide to EtherNet/IP Network Design,” cited in Industrial Ethernet media, distilled principles used at scale by large manufacturers such as General Motors. Combined with Rockwell Automation and Cisco CPwE guidance and Control Engineering articles, several recurring design themes emerge that apply directly to power and automation networks.

Segregate Control from IT While Still Connecting Them

An EtherNet/IP control network should usually have a single, well‑controlled connection to the plant’s corporate backbone rather than multiple uncontrolled cross‑links. ODVA‑aligned design examples use VLANs to keep control traffic logically separate from office traffic, even when they share physical switches.

Broadcast and multicast traffic should remain within defined VLAN boundaries. Inter‑VLAN traffic is routed, not just switched, which makes it easier to inspect, filter, and secure. Rockwell Automation’s guidance for plant‑wide EtherNet/IP emphasizes an Industrial Demilitarized Zone (IDMZ) and firewalls between enterprise and industrial zones. That gives you data sharing—for example, historian access to UPS events and power quality data—without exposing your control VLANs directly to office traffic or the wider internet.

In practice, I recommend placing your critical power protection devices—UPSs, inverters, static transfer switches, intelligent switchgear—into dedicated industrial VLANs under a Cell/Area zone, then carefully defining what traffic is allowed between that zone and the rest of the plant and enterprise.

Right‑Size and Segment: Broadcast Domains, Subnets, and Addressing

Right sizing an EtherNet/IP network means giving it its own subnets and broadcast domains, sized to the control applications they support, instead of dumping everything onto one plant‑wide flat LAN. The ODVA‑aligned architecture described in Industrial Ethernet publications uses this approach so that broadcasts land only on EtherNet/IP devices that need them.

Control Engineering recommends splitting logical topology into modular Layer 2 building blocks, often with VLANs limited to fewer than about 200 devices. That number is not a hard universal limit, but it reflects operational experience: bigger broadcast domains are harder to troubleshoot, more prone to storm‑like behavior if something misbehaves, and more likely to stress lower‑cost devices.

The same sources emphasize simple IP addressing, often with Class C ranges, so that plant personnel can easily understand and maintain the address plan. A “well‑architected” address space is one that technicians can sketch on a whiteboard and mentally map to the plant layout. A common pattern is to assign each machine line or power room its own subnet. For EtherNet/IP, that also makes it easier to reuse controller programs because I/O address blocks can stay consistent from line to line.

Give Control Traffic Absolute Priority

One of the most important principles from ODVA‑oriented design guidance is that EtherNet/IP implicit I/O traffic should have absolute priority over all other traffic, including IT and network management. Contention for the physical media is eliminated by using fully switched, full‑duplex Ethernet (no hubs, no half‑duplex links). Congestion, where multiple messages need the same link at the same moment, is handled with prioritization.

Ethernet provides eight priority levels in the VLAN tag priority field, from zero to seven. In practice, the authors argue that EtherNet/IP control systems do not need a complex hierarchy of queues. A two‑queue model is sufficient: one high‑priority queue for implicit control traffic and one low‑priority queue for everything else. Control messages are mapped into the high queue, and any time there is a conflict, those frames leave the switch first.

From a practical configuration standpoint, that means you mark EtherNet/IP I/O traffic with a high Class of Service value in your switches and ensure that every switch along the path has QoS enabled with at least two hardware queues. All other traffic—including engineering workstation file transfers, patch downloads, and even SNMP management—must defer to those control frames.

Choose Topologies and Redundancy With a Purpose

Modern EtherNet/IP plants rely on fully switched Ethernet. At the access layer, you typically see star or ring topologies. EtherNet/IP supports device‑level ring (DLR) topologies where devices form a ring and maintain communication even if a cable or single device fails. Bürkert notes that DLR helps maintain availability in rings by quickly detecting and compensating for breaks.

For higher levels, such as connecting power rooms to core switches, CPwE‑style designs use redundant fiber uplinks and ring or redundant‑star topologies. Control Engineering articles on EtherNet/IP deployment recommend combining such redundancies with protocols that prevent Layer 2 loops and deliver fast convergence, so that a link or switch failure does not cause timeouts in your PLCs or UPS controllers.

ODVA guidance also warns against adding redundancy everywhere “by default.” Redundant networks carry costs: extra hardware, complexity, and more challenging troubleshooting. The better strategy is selective redundancy where the value clearly exceeds the cost. For example, you might choose dual redundant paths and power supplies for UPS control and critical switchgear, but accept single paths for noncritical monitoring, such as lighting panels.

Use Industrial‑Grade Managed Switches and Quality Cabling

BizTech Magazine points out that every switch in a modern enterprise network should be managed and fully support SNMP; “web‑only” switches with no SNMP capabilities hinder central monitoring. In industrial EtherNet/IP networks, that recommendation is even more important. Managed industrial switches provide QoS, VLANs, multicast control, loop prevention, time synchronization, traffic statistics, and diagnostics that are essential for high uptime.

Industrial guidance from Rockwell Automation and others recommends using 1 Gbit/s fiber uplinks between switches and selecting cabling matched to environmental conditions and electromagnetic noise. Eoxs notes that upgrading to high‑grade cabling such as Cat6a or Cat7 improves signal integrity, while shielded twisted pair is useful in electrically noisy areas. For PoE‑powered devices like cameras or access readers around your power rooms, Phihong stresses matching PoE switch standards (such as IEEE 802.3bt for higher power) and cabling category to anticipated future loads, not just today’s devices.

In a typical power control room, that might translate into fiber links between the room and the core switch, shielded copper runs within the room, industrial managed switches at the local level, and PoE for auxiliary systems such as environmental sensors and IP cameras.

Follow a Structured Design Process, Not Ad Hoc Growth

Control Engineering’s “10 tips for deploying EtherNet/IP” and “Five tips to modernize industrial network architectures” emphasize that successful plant‑wide EtherNet/IP deployments start with understanding each networked device’s application and communication requirements. That includes traffic patterns (cyclic I/O vs sporadic diagnostics), industrial vs non‑industrial traffic types, required update rates, and future expansion plans. Those details belong in a network requirements document.

From there, Rockwell Automation and Cisco’s CPwE architectures provide validated Layer 2 and Layer 3 hierarchy models, zone definitions, and tested configuration patterns. The design process typically moves from logical topology—zones, VLANs, address ranges, security policy—to physical layout, overlaying the logical design on plant drawings and choosing media, switch locations, and paths that meet availability and resiliency targets.

An important part of that process is early collaboration across IT, OT, safety, and security. Control Engineering notes that upfront collaboration helps define required system connections (for example, MES to ERP), design maintainable networks, and identify risks before deployment rather than trying to retrofit security and segmentation later.

Traffic Types, Performance, and Monitoring

EtherNet/IP performance is a function of both network architecture and endpoint behavior. Several sources, including BizTech Magazine and Eoxs, converge on a few practical expectations for modern Ethernet.

Speeds, Errors, and Baselines

BizTech reports that nearly all access ports in a well‑managed network should run at 1000 Mbps full duplex. That is the baseline you should target for EtherNet/IP devices such as drives, controllers, and high‑bandwidth power quality meters. Some endpoints legitimately run at 100 Mbps—examples include older printers or devices that enter power‑saving modes—so your monitoring should treat those cases as known exceptions, not automatic faults.

Any new device connecting at 10 Mbps or half‑duplex, however, is a problem waiting to happen. Those modes usually indicate very old hardware or the presence of a hub, and they are not acceptable in a control network. Modern EtherNet/IP switches and devices should auto‑negotiate gigabit full‑duplex wherever possible. Forcing speed/duplex manually on gigabit links is discouraged because it often leads to mismatches and errors.

Modern Ethernet should be essentially error‑free. BizTech cites a real‑world case where a switch port carried more than 20 terabytes of traffic over eighteen months without a single error. That is the standard you should aim for. Any port registering errors should be treated as a symptom of either hardware issues, cabling faults, or misconfiguration. A good management system will poll port statistics frequently—every fifteen to sixty minutes across the network—and send daily or weekly summaries of ports with errors or abnormal speed/duplex settings.

Eoxs adds that continuous monitoring and maintenance are not optional. Network monitoring tools should track latency, bandwidth use, and error rates so that trends can be spotted before they become production incidents. That is especially important around power systems, where a network‑caused loss of visibility into a UPS during a disturbance can complicate root‑cause analysis.

Implicit I/O and Timing

Implicit I/O traffic on EtherNet/IP uses UDP to deliver periodic data with low overhead. For motion control or tightly coordinated systems, CIPSync and IEEE 1588 PTP are used to synchronize clocks to better than 100 nanoseconds, according to Embien. Control Engineering likewise recommends PTP for time synchronization, QoS for prioritizing control data, and IGMP for multicast management to minimize latency and jitter.

For power and protection applications, time sensitivity is usually not as extreme as sub‑microsecond motion control, but it is still significant. Protective relays, breaker interlocks, and transfer logic often depend on timely status updates. While the trip path may still be hard‑wired for safety, command confirmation, alarms, and logging typically traverse the EtherNet/IP network. Ensuring that those cyclic messages are prioritized and unaffected by bursty information traffic, such as SCADA trends or historian bulk transfers, is key.

Endpoint and NIC Settings

FlexRadio’s guidance on optimizing Ethernet adapters for high‑throughput SDR applications translates reasonably well to industrial PCs and HMIs acting as EtherNet/IP clients. Keeping NIC drivers up to date is one of the highest‑impact steps. Preventing Windows from powering off the Ethernet adapter for energy saving avoids mysterious disconnects when workstations go idle.

Energy Efficient Ethernet (EEE or “Green Ethernet”) can reduce link power usage during low activity, but if negotiation between switch and NIC is imperfect, it can cause poor throughput or dropped packets. FlexRadio recommends disabling EEE on both switch and NIC when you see data errors or disconnects. That same principle holds when an engineering workstation repeatedly loses EtherNet/IP sessions during load.

NIC settings such as receive and transmit buffers, receive side scaling, and offload options should be tuned to your use case. FlexRadio suggests increasing buffer sizes and enabling RSS to distribute receive processing across CPU cores. They also note that disabling certain offloads and interrupt moderation can reduce latency at the cost of slightly higher CPU usage. For EtherNet/IP engineering stations where responsiveness matters more than squeezing every last bit of throughput, those tradeoffs can be acceptable.

Converged Plantwide Ethernet and IT/OT Integration

Modern industrial IP networks are about more than just moving control traffic. Control Engineering highlights that smart manufacturing relies on real‑time KPI tracking, predictive maintenance, and lifecycle traceability. Gartner forecasts, cited in those discussions, suggested tens of billions of connected devices and trillions of dollars in value from IIoT.

That connectivity comes with risk. BDO USA data referenced in Control Engineering articles showed that more than ninety percent of manufacturers cited cybersecurity concerns in SEC filings, and the U.S. Department of Homeland Security has warned that many industrial organizations treat basic security as an afterthought. The recommended response is a defense‑in‑depth approach: multiple complementary layers of technical and procedural controls rather than reliance on a single product or obscurity.

Architectures like CPwE and the industrial designs promoted by firms such as Agilix focus on segmentation, redundancy, an IDMZ, industrial firewalls, secure remote access, and standardized protocols such as EtherNet/IP and TCP/IP to unify systems. That means your UPSs, inverters, drives, and PLCs can live in well‑defined OT zones, with hardened infrastructure layers that support fifteen‑ to twenty‑year lifecycles, yet still connect securely to cloud analytics or remote experts.

Workforce capability is part of that story. Control Engineering recommends leveraging training and certification programs such as Industrial IP Advantage eLearning to build expertise in converged IT/OT environments. Agilix likewise emphasizes staff certifications like CCNA, CCNP, and CISSP combined with vendor partnerships.

Applying EtherNet/IP Design to Power Protection Systems

From a power system reliability standpoint, EtherNet/IP network design is not an abstract exercise. It changes what happens under real faults.

Imagine a typical facility with a main UPS plant, several large inverters feeding critical loads, automatic transfer switches, and generator controls. Each of those systems has an EtherNet/IP or TCP/IP interface. You may also have drives for cooling systems, power quality meters, and protective relays talking to PLCs.

A robust architecture for this environment would give the power protection devices their own Cell/Area zone with dedicated VLANs and subnets. UPSs and inverters that exchange time‑sensitive status and commands with PLCs use implicit I/O mapped into high‑priority QoS queues. SCADA and engineering stations access those same devices over explicit messaging, but their traffic is treated as lower priority.

DLR or ring topologies within the power room provide resilience against a single cable or switch failure, while redundant fiber uplinks connect the power room to the plant core. The plant core, in turn, connects through an IDMZ and firewalls to the enterprise, allowing historians and analytics platforms to consume power data without exposing the control VLANs.

PoE equipment may power access control, IP cameras, and environmental sensors around critical rooms. Phihong recommends designing PoE infrastructure with future standards in mind—selecting switches and injectors that support high‑power devices under IEEE 802.3bt and pairing them with higher‑category cabling. That way, as you add higher‑power sensors, smart lighting, or additional cameras, you do not need to rebuild the underlying cabling or switch layers.

Monitoring tools poll SNMP on every managed switch port, as BizTech advocates, collecting errors and speed/duplex information every few minutes. Automated daily reports highlight any port with non‑gigabit speeds, half‑duplex, or errors, and each one is investigated—before a problem manifests during a utility outage.

Security controls follow defense‑in‑depth. The industrial zone has its own security policy, aligned but not identical to the enterprise policy. Firewalls enforce traffic rules between zones. Remote access is authenticated and encrypted, and VLANs are used to isolate sensitive control systems from less critical networks. That allows you to expose, for example, read‑only UPS status to a corporate dashboard without granting write access from the enterprise network into the control VLAN.

When designed and operated this way, EtherNet/IP becomes an asset to power system reliability rather than a vulnerability.

FAQ: Practical Design Questions

Can I put UPSs, drives, and IT devices on the same switch?

You can, but the more important question is whether they share the same VLANs and QoS treatment. Following ODVA‑style guidance, it is better to place EtherNet/IP control devices in dedicated VLANs and give their implicit I/O traffic absolute priority, even if they share physical switch hardware with other networks. Using separate VLANs, clear QoS rules, and an IDMZ gives you the benefits of shared infrastructure without the risks of an unsegmented flat network.

Do small EtherNet/IP systems really need managed switches?

Experience and industry guidance say yes. Even in relatively small networks, managed industrial switches provide VLANs, QoS, IGMP, PTP, loop prevention, and diagnostic visibility you cannot get from unmanaged devices. BizTech’s observation that every enterprise switch should support SNMP applies doubly in industrial settings, where proactive monitoring of errors and link states is critical. For power systems, a single unmanaged switch acting as a hidden bottleneck or single point of failure is an unnecessary risk.

When should I use ring topologies versus a simple star?

For local device‑level networks, such as a set of EtherNet/IP I/O blocks or drives in a panel, a DLR ring can provide fast recovery from a single break with minimal extra configuration. For higher‑level aggregation, CPwE‑style redundant stars or rings with well‑understood resiliency protocols are a good fit. ODVA‑related guidance suggests using redundancy where its value clearly exceeds its complexity and cost. For example, a DLR ring for control of a critical UPS plant is justified, whereas a simple star may be adequate for noncritical monitoring networks.

Closing Thoughts

A power system is only as reliable as the control and communication fabric that surrounds it. EtherNet/IP gives you an open, Ethernet‑based protocol stack that integrates cleanly with IT networks while still meeting real‑time industrial needs—if you architect it deliberately. By treating EtherNet/IP control traffic as first‑class, segmenting and right‑sizing your networks, choosing industrial‑grade hardware, and monitoring continuously, you can turn your Ethernet infrastructure into a dependable backbone for UPS systems, inverters, and power protection equipment rather than a hidden weak link.

References

1. https://www.odva.org/wp-content/uploads/2020/05/PUB00035R0_Infrastructure_Guide.pdf
2. https://www.plctalk.net/forums/threads/ethernet-ip-performace-tips.47918/
3. https://www.controleng.com/10-tips-for-deploying-ethernet-ip-the-odva-ethernet-protocol/
4. https://www.embien.com/industrial-insights/the-essential-guide-to-the-odva-ethernet-ip-protocol
5. https://www.naddod.com/blog/comprehensive-guide-to-high-performance-networking?srsltid=AfmBOoqY-KAP6e7HbPxadNH4Mj4ip743J0ebCcsTy2GktGNuI14D52kn
6. https://www.phihong.com/how-to-build-a-future-proof-ethernet-infrastructure-designing-and-implementing-a-reliable-poe-network-for-modern-businesses/
7. https://pyramidsolutions.com/ethernet-ip-essentials-elevating-your-network-infrastructure/
8. https://www.amazon.com/EVERYMANS-GUIDE-ETHERNET-NETWORK-DESIGN/dp/B0B7PSHK7J
9. https://www.ciena.com/insights/articles/The-top-6-features-of-a-truly-future-proof-converged-Ethernet-and-IP-network.html
10. https://eoxs.com/new_blog/top-techniques-for-optimizing-your-industrial-ethernet-network-performance/