Extreme Networks ExtremeWare XOS Guide Manual page 143

• Engineering is the carrier VLAN on STPD2.
• Marketing is a member of both STPD1 and STPD2 and is a protected VLAN.
Figure 9: Multiple Spanning Tree domains
Sales, Personnel, Marketing
Switch A
Switch B
Sales, Personnel, Manufacturing, Engineering, Marketing
When the switches in this configuration start up, STP configures each STPD such that the topology
contains no active loops. STP could configure the topology in a number of ways to make it loop-free.
In Figure 9, the connection between switch A and switch B 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 protected 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 10 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 XOS 10.1 Concepts Guide
STPD 1
Manufacturing, Engineering, Marketing
Switch M
STPD 2
STP Configurations
Switch Y
Switch Z
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