Port diagnostics

Port diagnosis can be used to identify the neighboring PROFINET devices. The device's own port can also be diagnosed.

Local Port Data and Remote Port Data

The information here is subdivided into local port information and remote port properties. In PROFINET the LLDP protocol (IEEE Std 802.1AB) is mandatory from conformance class A (CCA). The devices exchange neighborhood IDs via this protocol, so that each port is known to its neighbor. Furthermore, the Simple Network Management Protocol (SNMP) can be used as an aid at this point.
On opening the Port Diagnosis tab, TwinCAT acts as a Network Management Station (NMS) and collects the required device information via SNMP. In the previous image, you can see, for example, properties of the local port, data of the neighboring device and port statistics.

For correct topology recognition it is important that only devices are present in the segment that also support the LLDP protocol (this also applies to switches).

There is a possibility that there may be unwanted behavior in Windows 10. This is reflected in inconsistencies in topology detection.

Inconsistencies in topology detection.
Windows 10 provides an LLDP driver which is active by default. The PROFINET device also contains an LLDP driver. The system then sends two LLDP telegrams from one port to the remaining nodes on the bus. These remaining devices also expect two ports due to two LLDP telegrams, which do not exist.
To prevent this behavior, disable the Windows LLDP driver. To do this, uncheck Microsoft-LLDP-Driver (see red rectangle).