Definition of BPDU
The BPDUs are frames containing information on the Spanning Tree Protocol (STP). The transfer is sent to MAC (1:80: C2:00:00:00 or 1:00:0C: CC: CC: CD for the proprietary Cisco Per VLAN Spanning Tree) using the unique source address MAC of its port of origin.
The 802.1D spanning tree has two types of BPDUs:
BPDU setup to be sent to all switches via root bridges.
The TCN (Notification of Topology Change) is sent via bridges to the root bridge to record topology changes, such as port up or port down.
The BPDU is shipped every 2 seconds by default.