Why is the "S-Bus Master IP" FBox LED red after some time?

FAQ #101286

 

Symptom
When establishing Ether-S-Bus communication, the communication works fine, but the S-BUS Master IP FBox is turned into red. No no communication problems are observed and registers, flags, etc. are transmitted correctly. But after some time the LED of the "S-BUS Master IP" FBox turns to red.
After a 'Restart cold all' of the CPU, the FBox gets green again.

Reason
On IP-networks, it's absolutely normal that communication retries of telegrams can happen from time to time (due to telegram losts). In this case, the PCD will re-try to send/receive the media automatically.
However, the FBox will indicate every retry with a red LED. Therefore, the red S-BUS Master IP FBox has to be considered only as a warning/information.

Solution
As the loss of a telegram from time to time there is no action required as long as only one retry is executed.
You can check the retry-counter in the Diagnostic FBox of the S-Bus communication library to find out that you're in this kind of situation.