Within our network all switches use Spanning-Tree in orde to provide failover would a switch failure occur. Although we monitor each switch separately i always had the need to monitor the STP port states and see if one of the ports/trunks did a failover (and then, why).
After searching for a while i tried using SNMP to find the state and found it;
1 = Forwarding (active)
2 = Blocking (ment for failover)