In small and mid-sized automation projects, one question about EtherNet/IP networks keeps coming back: is an unmanaged switch good enough? A control cabinet typically holds a PLC, an HMI, and a few variable-frequency drives — a dozen or so devices sharing one network. Budget is limited, and a managed switch adds both purchase price and configuration time. At the same time, going unmanaged raises a quieter worry: when something stops communicating, how much harder will it be to find out why, with no traffic statistics and no diagnostics to look at? There is no single right answer for every site, but there is a clear method for reaching one.

Start with one technical trait of EtherNet/IP. Its real-time I/O data (implicit messaging) travels as multicast frames. An unmanaged switch has no IGMP Snooping, so a multicast frame received on one port is simply forwarded out of every other port — a flood. Every device on the network receives it, whether it needs that data or not. On a small network the wasted bandwidth is negligible and this behavior is harmless. As nodes multiply and links grow busier, the flooded frames begin competing with real-time I/O traffic for the same bandwidth, and the difference between the two switch types starts to show. The managed-versus-unmanaged decision is therefore about network scale and management needs, not about price alone.

Three steps keep the decision straightforward.

Step 1 — draw the topology and count the nodes.Map every link from the control cabinet out to the field devices. Count how many devices sit under each switch, how many switches the whole network contains, and how many levels of cascading exist between them. A dozen to twenty-plus nodes, one or two switches, arranged in a star or a simple cascade: this is the most common shape of an EtherNet/IP network, and an unmanaged switch carries it without strain. The drawing also shows where a failure would hurt most — which links carry the traffic of many devices at once, and where a single point of failure would take out a whole section. Small, flat, single-machine networks simply have no traffic that needs steering.

Step 2 — check for three hard requirements.These three map directly onto the two capabilities an unmanaged unit does not offer: control over how traffic flows across the network, and visibility into what is happening on it. If any one of them applies, a managed switch is the right choice.

① Multicast management. Once the node count reaches the scale of dozens, or when HMI traffic and real-time I/O share the same links, IGMP Snooping is needed to deliver multicast only to the ports that actually want it. Otherwise bandwidth is steadily consumed by frames that no device on those links needs.

② Redundant topology. A ring that has to recover from a broken link within tens of milliseconds depends on protocols such as ERPS or RSTP. Those protocols are managed-switch capabilities; an unmanaged unit cannot participate in them. In plants where a line stoppage is expensive, this is usually the deciding requirement.

③ Diagnostics and isolation. Port mirroring for packet capture, per-port traffic counters, and VLANs that separate different segments of traffic are all management functions. When fault-finding relies on this kind of visibility — knowing which port carried what, and when — an unmanaged switch offers nothing to work with.

Step 3 — put maintenance cost into the comparison.An unmanaged switch saves more than its price tag: configuration, training, password and firmware management, and everyday upkeep all disappear. Management features only pay for themselves once a network has grown too large to troubleshoot with port LEDs and common sense. Ownership matters as much as cost. Small sites rarely have a dedicated network engineer: the switch is installed by the machine builder and looked after by the maintenance crew. A managed unit left unconfigured or misconfigured can cause the very downtime it was meant to prevent, while a plug-and-play unit keeps behaving predictably. Replacement tells the same story — swapping a failed unmanaged switch takes minutes and needs no configuration backup, whereas a managed unit has to be replaced by an identically configured one or reconfigured on the spot. A practical test helps here. In the current topology, when a device drops offline, can the cause be located quickly by reading the port LEDs on the switch? If it can, the extra features will sit unused, and paying for them is hard to justify. If it cannot, that gap in visibility is the real reason to move up.

Bring this back to the typical small line. A dozen devices, one switch inside the cabinet, no ring requirement — for this kind of EtherNet/IP network, an industrial unmanaged switch is enough. The PUSR USR-ISG series fits this pattern: 5-port or 8-port gigabit models (100/1000 Mbps), plug-and-play with no configuration step before first use; redundant power inputs accepting DC 9.6 to 60 V; wide-temperature operation from −40 °C to +85 °C; a fanless aluminum housing rated IP40; DIN-rail mounting; and 6 kV surge protection on both power and network ports. The series holds 3C, CE, FCC, and ROHS certifications. It powers up, the cables plug in, and the line runs — commissioning time is spent on the PLC and the drives, not on the switch.

Before choosing an Industrial Ethernet Switch, draw the topology, count the nodes, and run through the checklist above. Most small and medium EtherNet/IP networks arrive at the same conclusion: put the budget into hardware that is reliably built for the environment first, and move to a managed switch later, when the network has grown to the point where its management features are genuinely needed.