Allied Telesis AT-GS950/48, User Manual

Page: 382 / 410

Appendix A: MSTP Overview
382
Multiple Spanning Tree Regions
Another important concept of MSTP is regions . An 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. Practically, however, it is 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 considers the
bridges as residing in different regions.
Table 7 on page 383 illustrates the concept of regions. It shows one MSTP
region consisting of two AT-GS950/48 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.