What CIP Is
The Common Industrial Protocol (CIP) is an application-layer protocol managed by the ODVA. It defines the object model, services, and messaging framework shared by EtherNet/IP, DeviceNet, and ControlNet.
CIP defines what data is exchanged and how — the underlying network transport (Ethernet, CAN, etc.) is handled by the specific transport protocol.
CIP Object Model
CIP organizes device functionality into objects:
| Object | Purpose |
|---|---|
| Identity Object | Device name, vendor, serial number |
| Assembly Object | Groups I/O points for data exchange |
| Connection Manager | Manages communication connections |
| Message Router | Routes messages to the correct object |
Messaging Types
| Type | Transport | Use |
|---|---|---|
| Explicit (Class 3) | TCP | On-demand reads, configuration, diagnostics |
| Implicit (Class 1) | UDP | Cyclic I/O exchange at fixed intervals |
Most QuickServer and FieldServer gateway integrations use explicit messaging for simplicity and flexibility.
CIP Ports
| Port | Protocol | Use |
|---|---|---|
| TCP 44818 | EtherNet/IP | Explicit messaging |
| UDP 2222 | EtherNet/IP | Implicit (I/O) messaging |
[!NOTE] Firewalls must allow both TCP 44818 and UDP 2222 for full EtherNet/IP functionality. Blocking either port causes partial communication failures.