EtherNet/IP — CIP over Ethernet
EtherNet/IP runs the Common Industrial Protocol (CIP) over standard Ethernet. The scanner (master) and adapter (slave) exchange CIP messages wrapped in EtherNet/IP encapsulation. Distinctive trait: each chip carries a colored marker stripe on its head indicating which CIP layer it belongs to — ENIP / CPF / CIP-Conn / CIP-Svc rotate across the 4 stripe colors.
Animation
Engineering pitfalls
Class 1 RPI faster than network can sustain
Requested Packet Interval (RPI) defines how often the IO connection refreshes. Set too aggressive (≤2 ms) on a saturated 100 Mbps link and you'll see timeouts. Test with the actual production load before commissioning.
EDS file vs device firmware mismatch
EDS (Electronic Data Sheet) files describe the device's CIP object dictionary. An EDS from the vendor site may lag the device's actual firmware. Always pull EDS from the device via the configuration tool.
Connection-Manager timeout multiplier under-provisioned
The CIP timeout multiplier × RPI = how long the connection waits before declaring loss. Under-provisioned timeouts in noisy environments cause spurious dropouts; over-provisioned masks real failures. Audit per facility.
UDP port 2222 vs TCP port 44818 confusion
Class 1 IO uses UDP/2222. Class 3 explicit messages use TCP/44818. A firewall that allows only TCP/44818 silently breaks Class 1 IO without any obvious error. Verify both ports.
References
Primary sources
- ODVA — The CIP Networks Library, Volume 2 (EtherNet/IP Adaptation of CIP).
- ODVA Publication PUB00213R0 — EtherNet/IP Quick Start.
- IEEE 802.3 — Standard for Ethernet.