Extreme Networks ExtremeWare 7.2e Installation And User Manual page 199

Figure 31: Multiple Spanning Tree Domains
Sales, Personnel, Marketing
Switch A
Switch B
STPD 1
Sales, Personnel, Manufacturing, Engineering, Marketing
When the switches in this configuration start up, STP configures each STPD such that there are no
active loops in the topology. STP could configure the topology in a number of ways to make it loop-free.
In Figure 31, the connection between switch 1 and switch 2 is put into blocking state, and the
connection between switch Y and switch Z is put into blocking state. After STP converges, all the
VLANs can communicate, and all bridging loops are prevented.
The VLAN Marketing, which has been assigned to both STPD1 and STPD2, communicates using all five
switches. The topology has no loops, because STP has already blocked the port connection between
switch A and switch B, and between switch Y and switch Z.
Within a single STPD, you must be extra careful when configuring your VLANs. Figure 32 illustrates a
network that has been incorrectly set up using a single STPD so that the STP configuration disables the
ability of the switches to forward VLAN traffic.
ExtremeWare 7.2e Installation and User Guide
Manufacturing, Engineering, Marketing
Switch M
STPD 2
STP Configurations
Switch Y
Switch Z
ES4K016
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