• atulsharma.cse@gmail.com
• November 23, 2014
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Two Types of BPDUs

To this point, the chapter has referred to all BPDUs as a single type. Actually, there are two
types of BPDUs:
? Configuration BPDUs
? Topology Change Notification (TCN) BPDUs
Configuration BPDUs are originated by the Root Bridge and flow outward along the active
paths that radiate away from the Root Bridge.

Topology Change Notification BPDUs flow
upstream (toward the Root Bridge) to alert the Root Bridge that the active topology has
changed. The following sections discuss both of these BPDUs in detail.