Extreme Networks ExtremeWare XOS Command Reference Manual page 1173

ExtremeWare XOS 11.5 supports only the Summit X450 family of switches and the BlackDiamond 8800 series switch.
configure mstp region
region, the number or tag that identifies all of the BPDUs sent in the MSTP region, and the reserved
MSTP revision level. If configured, the output also displays the name of the Common and Internal
Spanning Tree (CIST), and the number of Multiple Spanning Tree Instances (MSTIs).
Example
The following command creates an MSTP region named purple:
configure mstp region purple
History
This command was available in ExtremeWare XOS 11.4.
Platform Availability
This command is available on all platforms.
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ExtremeWare XOS 11.5 Command Reference Guide