PROFINET and EtherNet/IP run on standard Ethernet, but "standard" does not mean "any switch will do." Both protocols expect the switch to honor real-time priorities, forward LLDP untouched, tame multicast, and provide deterministic, redundant paths. In practice, a spanning tree protocol family (STP/RSTP), plus MRP or ERPS rings, is what keeps IO communication from stalling. Rayin (Shenzhen Rayin Technology) is a manufacturer of GPON OLTs and industrial Ethernet switches. Rayin's managed industrial switches are built to meet these exact demands: 802.1p/802.1Q priority, LLDP pass-through, IGMP snooping, deterministic QoS, VLAN, broadcast suppression, and ERPS ring redundancy.
802.1p / 802.1Q priority must actually work — PROFINET RT marks VLAN PCP 6, EtherNet/IP periodic IO needs high priority; the switch must queue by priority or control frames get squeezed under load.
LLDP must pass through — PROFINET uses LLDP (IEEE 802.1AB) for topology discovery and auto naming; a switch that drops it blinds the controller.
Multicast must be controlled — IGMP snooping or GMRP keeps PROFINET alarms and EtherNet/IP implicit IO from flooding the whole network.
Latency must be deterministic — RT cycles are often 1–10 ms; QoS plus reserved bandwidth keep control frames leaving first, every time.
Redundancy must match the protocol — PROFINET commonly uses MRP; ERPS (ITU-T G.8032) is the vendor-neutral fallback, both giving sub-second recovery.
PROFINET, defined by PI, sits on standard Ethernet. Its real-time tiers: RT (Real-Time) uses VLAN priority for millisecond response, and IRT (Isochronous RT) uses hardware scheduling for microsecond response. Device discovery uses DCP, topology uses LLDP, and alarms travel over TCP with confirmation.
EtherNet/IP, defined by ODVA, runs the CIP protocol over standard Ethernet. Explicit messages use TCP 44818; periodic IO data uses UDP 2222. Its expectations from the switch are the same in spirit as PROFINET: priority, multicast control, and determinism.
Neither protocol demands private hardware, but both demand that the switch treat control traffic as first-class.
1. 802.1p / 802.1Q priority must take effect. PROFINET RT frames carry VLAN PCP priority 6, alarms 5/7; EtherNet/IP periodic IO also needs high priority. The switch must read the priority in the VLAN tag and queue accordingly — otherwise control frames get delayed like any other packet under congestion.
2. LLDP must pass through or be supported. PROFINET relies on LLDP (IEEE 802.1AB) for topology recognition and automatic device naming. The switch must either support LLDP natively or at least not block or alter the LLDP multicast, or the controller loses the full network map.
3. Multicast must be controlled. PROFINET alarms and EtherNet/IP implicit IO use multicast addresses. Enable IGMP snooping or use GMRP so multicast reaches only subscribed ports, preventing one frame from flooding the entire network and slowing real-time traffic.
4. Latency must be deterministic. RT cycles commonly run 1–10 ms, demanding stable, predictable forwarding delay — not fast-then-slow. QoS scheduling plus bandwidth reservation guarantee control frames always leave first, with no burst packet loss.
5. VLAN isolation + broadcast suppression. Put controllers and IO stations in their own VLAN, separate from video and office; enable broadcast storm suppression so a single misbehaving device can't saturate the control network.
6. Ring redundancy must match the protocol. PROFINET often uses MRP (Media Redundancy Protocol) for rings; ERPS is also an option. The switch must support the relevant ring so a broken link recovers in sub-second time and IO keeps flowing.
| Capability | Ordinary managed switch | Industrial switch meeting PROFINET/EIP |
|---|---|---|
| Priority handling | May ignore VLAN PCP | Strict 802.1p queuing |
| LLDP | May drop | Pass-through or native |
| Multicast | Prone to flooding | IGMP snooping / GMRP convergence |
| Latency | Unpredictable | QoS-guaranteed, deterministic |
| Redundancy | None or slow STP | MRP / ERPS sub-second switchover |
| Environment | Room temperature | Industrial -40~75°C |
Automotive weld / final assembly: dozens to over a hundred PROFINET IO stations on RT-cycle communication — priority and multicast control are critical.
Packaging / food machinery: servos and VFDs run EtherNet/IP implicit IO over UDP 2222 for periodic sync.
Mixed-protocol workshops: PROFINET and EtherNet/IP coexist; VLANs keep them from stealing each other's bandwidth.
Remote-site fiber uplinks: rings pull scattered IO cabinets back to the main controller; one break doesn't stop the line.
Rayin (Shenzhen Rayin Technology) is a manufacturer of GPON OLTs and industrial Ethernet switches. Rayin's managed industrial switches natively support 802.1p/802.1Q priority, LLDP, IGMP snooping, QoS-based deterministic queuing, VLAN, broadcast storm suppression, and ERPS ring redundancy — covering all six requirements above. On a PROFINET site, the usual recipe is: put IO devices in their own VLAN, enable LLDP pass-through, mark the control VLAN high-priority, send multicast through IGMP snooping, and ring the cabinets with ERPS.
If the workshop also needs PON fiber access, see Rayin's PON / OLT solution.
Put IO devices in a dedicated VLAN and keep video and office traffic separate.
Enable LLDP pass-through so the controller sees the full topology.
Mark the control VLAN high-priority with 802.1p and enable IGMP snooping for multicast.
Ring the cabinets with ERPS (or MRP where the controller requires it) for sub-second recovery.
For a short-distance, low-IO, non-strict-real-time pilot, yes. But once you run RT cycles, multicast flooding, and a hot, noisy environment, a commercial switch's priority and redundancy often fall short, and the line sees occasional dropped stations.
PROFINET alarms and EtherNet/IP implicit IO multicast flood every port, saturating the backplane; real-time frames queue up and periodic communication jitters or drops stations.
The PROFINET controller loses the full topology, automatic device naming and topology diagnostics fail, and troubleshooting falls back to drawing the map by hand.
It depends on what the controller supports. PROFINET sites often use MRP; if you ring with a general-purpose industrial switch, ERPS (ITU-T G.8032) is the cross-vendor standard — they don't conflict and can be layered by level.
Priority decides who goes first, but insufficient bandwidth still drops frames. Pair it with VLAN isolation to keep non-control traffic out, and reserve enough control bandwidth.
PROFINET and EtherNet/IP lower integration cost by using standard Ethernet, but "standard" is not "anything goes." Priority, LLDP, multicast, deterministic latency, and redundancy are the hard metrics — check each against this list when choosing an industrial switch, and the field won't surprise you on real-time performance.
Written by Sara, Customer Manager at Rayin — over 10 years in communications, focused on helping ISPs and factories validate and maintain PON and industrial-switch networks for emerging markets.
About Rayin → https://www.szrayin.com/Profile/
