Master Bridge Protocol Data Unit (BPDU) Frame Format: Complete Guide to 802.1D STP (Updated November 2025)
In CCNA labs, spotting a BPDU storm can crash your network—understanding the frame format is your first line of defense.. The spanning tree algorithm exchanges the Bridge Protocol Data Unit (BPDU) to elect the Root Bridge. It is a frame containing 12 different fields with different information. The information in the BPDU is used to