Allied Telesis AT-GS950/8 - Manual (Page 384)

Appendix A: MSTP Overview
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Here is an example. Assume that you have two regions that contain the
following VLANS:
Region 1 VLANs Region 2 VLANs
Accounting Accounting
Sales Sales
Pre-Sales Pre-Sales
Marketing Technical Support
Product Management Software Engineering
Project Management Hardware Engineering
The 2 regions share 3 VLANs: Accounting, Sales, and Presales. You can
group these 3 VLANs into the same MSTI in each region. For instance, for
Region 1 you might group the 3 VLANs in MSTI 12, and in Region 2 you could
group them into MSTI 16. After they are grouped, you can connect the VLANs
across the regions using a link of untagged/tagged ports as shown in Figure
160.
Figure 160. Spanning Regions without Blocking
Switch A
Switch B
Region 1 Region 2
Port 6
MSTI 12
VLAN (untagged) port: Accounting
VLAN (tagged port): Sales
VLAN (tagged port): Pre-Sales Port 1
MSTI 16
VLAN (untagged) port: Accounting
VLAN (tagged port): Sales
VLAN (tagged port): Pre-Sales