Specifications

CHAPTER 3
Spanning Tree
Bridge Protocol Data Units
Switches exchange Bridge Protocol Data Units (BPDU). The two types of BPDUs are Configuration and Topology
Change Notification(TCN). Configuration BPDUs are sent every two seconds from the root toward the downstream
switches. They:
n Are used during an election
n Maintain connectivity between switches
n Send timer information from the root
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CCNP SWITCH 642-813 Quick Reference by Denise Donohue
FIGURE 3-2
The Active Topology
After Spanning Tree
Is Complete
A
BC
D
E