Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 481)

Spanning Tree Introduction: STP, RSTP, and MSTP
Software Reference for x310 Series Switches
C613-50046-01 REV A AlliedWare Plus TM Operating System - Version 5.4.4C 18.13
MSTP Regions
An MST region is a set of interconnected switches that all have the same values for the
following MST configuration identification elements:
■ MST configuration name - the name of the MST region
■ Revision level - the revision number of configuration
■ Configuration Digest - the mapping of which VLANs are mapped to which MST
instances
Each of the MST instances created are identified by an MSTI number. This number is locally
significant within the MST region. Therefore, an MSTI will not span across MST regions.
Figure 18-2: MSTIs in different regions
The task of assigning each bridge to a particular region is achieved by the member
bridges each comparing their MST Configuration Identifiers. More information on
configuration identifiers is provided in
Table 18-6 , but for the moment an MST
Configuration Identifier can simply be thought of as an identifier that represents the
mapping of VLANs to MSTIs within each bridge. Therefore, bridges with identical MST
Configuration Identifiers, must have identical MSTI mapping tables.
MSTI1
MSTI2
MSTI3
MSTI_numbers
MSTI1
MSTI3
MSTI2
MSTI4
Region 1
Region 3
Region 2
The MSTI1 in Region 1 is unrelated to the MSTI1 in Region 3. Similarly, the MSTI2 in Region 1 is quite
unrelated to the MSTI2 in Region 2.
Physical connections