3Com 8807 Configuration Manual page 127

Introduction to MSTP 127
Figure 28 Designated bridge and designated port
Switch A
AP1 AP2
CP1
BP1
Switch C
Switch B
CP2
BP2
LAN
For a switch, the designated bridge is a switch in charge of forwarding BPDU to
the local switch via a port called the designated port accordingly. For a LAN, the
designated bridge is a switch that is in charge of forwarding BPDU to the network
segment via a port called the designated port accordingly. As illustrated in the
Figure 28, Switch A forwards data to Switch B via the port AP1. To Switch B, the
designated bridge is Switch A and the designated port is AP1. In the figure, Switch
B and Switch C are connected to the LAN and Switch B forwards BPDU to LAN. So
the designated bridge of LAN is Switch B and the designated port is BP2.
The specific calculation process of STP algorithm.
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The following example illustrates the calculation process of STP.
Figure 29 illustrates the practical network.