Dell POWEREDGE M1000E - Manual (Page 635)

Configuring the Spanning Tree Protocol 635
How Does MSTP Operate in the Network?
In the following diagram of a small 802.1d bridged network, STP is necessary
to create an environment with full connectivity and without loops.
Figure 22-1. Small Bridged Network
Assume that Switch A is elected to be the Root Bridge, and Port 1 on Switch
B and Switch C are calculated to be the root ports for those bridges, Port 2 on
Switch B and Switch C would be placed into the Blocking state. This creates a
loop-free topology. End stations in VLAN 10 can talk to other devices in
VLAN 10, and end stations in VLAN 20 have a single path to communicate
with other VLAN 20 devices.
Switch A
Switch B
Switch C
Port 1
Port 1
Port 2
VLAN 20 VLAN 10
VLAN 20
VLAN 10
VLAN 20
Port 2
Port 2
Port 1