STP stabilizes the network into a loop free topology by causing some interfaces to simply not forward or receive traffic. Ports that are not passing traffic are considered to be in a Blocking State, where ports that ARE passing traffic are considered to be in a Forwarding State. The ports that are in a Forwarding state provide the loop free path over the network.
STP Protocol messages are called BPDU’s (Bridge Protocol Data Units)
This value is set to 0x0000
This value is set to 0x00
This field identifies the types of BPDUs: Configuration BPDUs (0x00) ot Topology Change Notification BPDUs (0x80)
This field uses 2 out of 8 bits to handle topology change acknowledgement and the topology change flag
Root Bridge ID and Root Path Cost
These fields identify the root bridge in the network
Sending Bridge Id and Sending Port Id
Includes the senders own bridge identifier and the port on the sender that actually fowrarded the BPDU
This is an estimate of the BPDUs age
Max Age, Hello Time, and Forward Delay
These timers always reflect the timer settings configured on the root switch.