Abstract: Presented herein are embodiments for tracing paths of packet flows in a data center fabric network. Filters are configured on nodes (e.g., switches) in the data center fabric network for a particular packet flow. Numerous such filters can be configured on each of the switches, each filter for a different packet flow. When a filter detects a match, it sends a log of such occurrence to a network controller. The network controller uses log data sent from nodes as well as knowledge of the network topology (updated as changes occur in the network) to determine the path for a particular packet flow in the data center fabric network. This technique works inline on the actual packet flow and does not need additional debug packets to be injected. This technique can also quickly point out the problem node in case of traffic drop.