NI-XNET Port LED Blinks Red

Solution

The port LED blinks red if a NI-XNET catastrophic error occurs as indicated in the NI-XNET manual.

There are several reasons for this issue:

Verify that the cabling is working properly.
Perform a loop-back test by using the Loopback Test.vi, located in the NI Example Finder in Hardware Input and Output >> CAN >> NI-XNET >> Loopback Test to verify correct cabling.
Check the termination resistors section in the device Getting Started Guide to verify that the termination resistors match the nominal impedance of the CAN cable. The termination resistance may become out of tolerance to support both devices.
Monitor the traffic on your bus using the NI-XNET Bus Monitor and ensure that Bus Error Frames are enabled in the Interface and Database Settings. You may see a Bus Error Frame which will have ERR as the frame type. You can reference the data in the frame payload against the Bus Error Frame chart to see the type of Bus Error that is occurring. If you are using CAN FD, it could be related to Error or Incorrect Frames When Using NI-XNET in CAN FD & BRS .
Verify that you are writing the right XNET messages.
If none of the above helps, contact NI Support.