Systems and methods are disclosed for identifying improper cabling of control system devices connected to redundant communication networks of distributed control systems. In an embodiment, a receiving device receives messages including a sender identification or source address, and a network or associated device port identification, from sending devices, over redundant networks. The receiving device determines a connect status indicating whether a message was received on a particular device port, and an error event indicating whether the port is associated with the network identified in the message. A system diagnoses an improper communication path between devices and produces an indication of a location and/or type of improper cabling. A method supplants error events with error rates calculated as a probability of receiving messages on a device port not associated with the network identified in a received message. The method compares the error rates to error thresholds to identify improper cabling.