Allied Telesis AT-S111 User Manual

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Appendix A: MSTP Overview
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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
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 AT-GS950/48PS switches. Each switch in the region has the 
same configuration name and revision level. The switches also have the same 
five VLANs and the VLANs are associated with the same MSTIs.