Appendix A: MSTP Overview
Multiple Spanning Tree Regions
Another important concept of MSTP is regions. A MSTP region is defined as a group of bridges that share exactly the same MSTI characteristics. Those characteristics are:
Region name
Region revision
VLANs
VLAN to MSTI ID associations
A region name is a name assigned to a region to identify it. You must assign each region exactly the same name for each bridge in that region; even the same upper and lowercase lettering. Identifying the regions in your network is easier if you choose names that are characteristic of the functions of the nodes and bridges of the region. Examples are Sales Region and Engineering Region.
The region revision is an arbitrary number assigned to a region. This number can be used to keep track of the revision level of a region’s configuration. For example, you might use this value to maintain the number of times you revise a particular MSTP region. It is important that each bridge in a region has the same region revision number. However, it is practically not important that you maintain this number.
The bridges of a particular region must also have the same VLANs. The names of the VLANs and the VIDs must be same on all bridges of a region.
Finally, each of the VLANs across the bridges must be associated to the same
MSTI IDs.
If any of the above information is different on two bridges, MSTP does consider the bridges as residing in different regions.
Table 10 illustrates the concept of regions. It shows one MSTP region consisting of two
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