Flow traffic in the web console is reviewed and it is noted that there is...

Comprehensive and Detailed Explanation From Exact Extract:

SolarWinds identifies and classifies flow traffic based on application and port mapping in the platform.

"Unclassified traffic in flow charts often occurs when an application is not mapped in the system, or when the application uses a port that is not defined in the SolarWinds Hybrid Cloud Observability (HCO) application mapping database. Flows from unsupported devices or flow direction do not cause unclassified application traffic—rather, they will not be collected or will be marked as unknown flows."

Thus, unclassified traffic can result from new or custom applications or changes in port usage that are not reflected in the configuration.