Engineering ReferenceEngineering Reference

EtherNet/IP

On this page

EtherNet/IP (“Industrial Protocol”) is an Ethernet implementation of the Common Industrial Protocol (CIP) stack maintained by ODVA. It is the dominant industrial protocol in the Rockwell Automation ecosystem.

Overview

  • Standard 100 Mb / 1 Gb Ethernet PHY (no special hardware required).
  • UDP port 2222 (implicit / I/O), TCP port 44818 (explicit).
  • Open spec; multi-vendor; certified by ODVA.
  • Coexists with normal IT traffic but should be on its own VLAN.

CIP Object Model

  • Objects expose Attributes via Services (Get_Attribute_Single, Set_Attribute_Single, etc.).
  • Class / Instance / Attribute addressing — every parameter is reachable.
  • Identity Object (0x01), Assembly (0x04), Connection Manager (0x06), TCP/IP Interface (0xF5), Ethernet Link (0xF6).
  • Device profiles standardize objects across vendors (e.g. Drives, Discrete I/O).

Implicit & Explicit Messaging

  • Implicit (I/O) — cyclic, UDP, low overhead; RPI typically 5–100 ms.
  • Explicit — TCP, on-demand, used for config / diagnostics.
  • Unicast or multicast for producer/consumer I/O (multicast needs IGMP snooping).
  • CIP Safety adds time-stamped, ID-verified messages for SIL3 / PLe.

Device Configuration

  • EDS file describes the device to the engineering tool.
  • Set IP (DHCP, BOOTP, static); avoid DHCP for production devices.
  • Add to Studio 5000 I/O tree; pick the correct connection (Exclusive Owner, Listen Only, Input Only).
  • Configure RPI per loop performance need; lower RPI = more bandwidth.

DLR & Redundancy

  • Device Level Ring (DLR) — sub-3 ms recovery on a physical ring of supervisor + ring nodes.
  • Each device needs DLR support; one supervisor (often the PLC).
  • Cable both ports of each device; close the ring at the supervisor.
  • For larger networks: ResilientEthernet (REP) or Spanning Tree.

Troubleshooting

  • Check ControlLogix module status LEDs and module properties > Connection tab for connection errors.
  • Wireshark with CIP dissector to capture explicit messages.
  • RSLinx Classic / FactoryTalk Linx to browse devices.
  • Watch packet rate vs RPI — exceeding the device’s spec causes dropped connections.
  • Common issue: duplicate IP; second cause: IGMP / multicast not configured on the switch.
reference page