Effects and Causes

PLC - Device object displays red symbol

It is imperative that you check the Controller status in the Status tab of the device.


See also

PLC - Device scan failed

In order for the scan dialog to show the PROFINET devices currently located in the PROFINET network, the data is read in two stages:

Possible problems:



PROFINET devices are displayed in the scan dialog, but not the modules of the devices.

The PROFINET device does not have an IP address, or it is located in another subnet than the controller and therefore it is unreachable via UDP.

The firewall is configured incorrectly. Another clue for this are error messages in the Log of the PLC.

Scan dialog displays nothing.

The driver is not started, and the application is stopped.

No PROFINET RT packets can be received.

See also

PROFINET slave device keeps red symbol

The controller is started and it is green (after about 3 sec.), but...


Cause / Background

...all configured PROFINET slaves remain red.

No connection to the network.

Issues with firewall. Check that the device scan functions correctly.

...a PROFINET slave remains red.

Device not in network. Check that the station name is correct.

Slave terminates the connection with errors.

Performance problems; the communication watchdog starts when establishing the connection.

...PROFINET slaves switch between green, red, and orange.

When establishing the connection, the symbol of the slave is an oranges triangle. The station status is Unknown.

If the Unknown state lasts for a long time before the symbol switches to red (error), then this means that the response from the slave is blocked by a firewall.

In the red/error state, the station status shows the causes. Typical errors are the causes are:




DNS unknown RealStationName

Incorrect station name device cannot be reached over the network (see


Connection aborted: AR consumer DHT expired

Transmit clock cannot be maintained (see 1.4, 1.3.3)


AR cmi timeout

Transmit clock cannot be maintained (see 1.4, 1.3.3)

... PROFINET slave is green, but it has a red exclamation mark, or individual modules are red.

The controller has an active connection, and therefore everything is okay.

The PROFINET device reports PROFINET diagnostic messages only for individual modules.

See also