Chapter 19 Troubleshooting : ­Troubleshooting tools : FortiOS diagnostics : Traffic trace
  
Traffic trace
Traffic tracing allows a specific packet stream to be followed. This is useful to confirm packets are taking the route you expected on your network.
View the characteristics of a traffic session though specific security policies using:
diag sys session
Trace per-packet operations for flow tracing using:
diag debug flow
Trace per-Ethernet frame using:
diag sniffer packet