Communication Timeout — EtherNet/IP

EtherNet/IP communication between PLC and remote device has timed out. CIP connection lost or I/O data exchange stopped.

Probable Causes (ranked)

• Ethernet cable disconnected, damaged, or wrong cable type (crossover vs straight-through)
• Network switch failure or port failure on switch
• Remote device crashed or locked up — needs power cycle
• IP address conflict — two devices with same IP on the network
• RPI (Requested Packet Interval) set too aggressive for network conditions
• PLC scanner module overloaded with too many connections

Fix Steps

1. 1 Check Ethernet cable connections at both PLC and remote device — reseat connectors
2. 2 Verify network switch port LEDs — link and activity should both be lit
3. 3 Ping the remote device IP address from a laptop on the same subnet
4. 4 Power cycle the faulted remote device — wait 30 seconds for full restart
5. 5 Check for duplicate IP addresses — review IP assignment spreadsheet or scan the network
6. 6 If using managed switch, check for VLAN or port security configuration blocking traffic
7. 7 Increase RPI timeout if connection drops intermittently under network load

Suggested Replacement Parts

Parts matched to fault category: Network Module

Prices are estimates. Verify part numbers match your equipment before ordering.

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