BPDU
In STP, a Bridge
Protocol Data Unit is a packet that initiates communication between devices. BPDU packets
contain information on ports, addresses, priorities, and costs and they ensure that the data
ends up where it was intended to go. BPDU messages are exchanged across bridges to detect
loops in a network topology. The loops are then removed by shutting down selected bridge
interfaces and placing redundant switch ports in a backup, or blocked, state.