>> The Root ID is the combination of bridge priority and base MAC Address as shown below:

>> There are 3 modes of STP

(a) MST (Multiple Spanning Tree)

(b) PVST (Per-VLAN Spanning Tree Mode)

(c) Rapid PVST

Rapid PVST uses IEEE 802.1w which gives a good package to all the issues which are addressed by using uplink fast, port fast and backbone fast commands. Others use IEEE 802.1d.

>> BPDU is Bridge Protocol Data Unit. These are the packets transferred between the switches with STP being enabled. These are used for the operation of STP.

>> If there is a topology change, the switch ports come in the state of listening and learning. In normal operation, the switch ports are in forwarding states. The topology change is determined by the BPDU Flag option as shown below:

>> The Root Bridge cannot have any blocked port. After convergence, all its ports come in the Forwarding state as shown below:

Root Bridge Output (Switch 1):

Non-Root Bridge Output (Switch 2):

To be continue …