This enumerated object controls whether mirroring of transmitted packets on a source interface depends on that interface's Spanning Tree Group forwarding state. Setting it to forwarding(2) mirrors only traffic actually transmitted while the port's STP instances are in the forwarding state, avoiding capture of packets during blocking or learning states, while no-care(1) mirrors transmitted traffic regardless of STP state. An admin troubleshooting only steady-state forwarded traffic on a redundant link would set dPktMonSessionSrcTxIfStgState to forwarding(2) so the capture ignores transient traffic seen while the port is still in STP learning state.