3Com 9100 - How STP Works

Overview of the Spanning Tree Protocol
89
If the link through Bridge C fails, as shown in Figure 15, the STP system
reconfigures the network so that traffic from segment 2 flows through
Bridge B.
Figure 15
Traffic flowing through Bridge B
How STP Works
STP has the following three stages of operation:
■
Initialization
■
Stabilization
■
Reconfiguration
Initialization
Initially, the STP system requires the following before it can configure the
network:
■
All bridges exchange information by way of Bridge Protocol Data Units
(BPDUs), which are transmitted in packets with a known multicast
address
■
To determine a single root bridge as a result of BPDU exchange
The Root Bridge is selected on the basis of it having the lowest Bridge
Identifier value. This value is a combination of the unique MAC address of
the bridge and a priority component defined for the bridge.