For multiple switches to be part of an MSTP region, you must configure each switch in the region with the same MSTP configuration attributes, also known as MSTP region identifiers. The following list describes the MSTP region identifiers:
Region Name—This indicates the name of the MSTP region. In the Extreme Networks implementation, the maximum length of the name is 32 characters and can be a combination of alphanumeric characters and underscores ( _ ).
Format Selector—This indicates a number to identify the format of MSTP BPDUs. The default is 0.
Revision Level—An unsigned integer encoded within a fixed field of 2 octets that identifies the revision of the current MST configuration. The revision number is not incremented automatically each time that the MST configuration is committed.
The switches inside a region exchange BPDUs that contain information for MSTIs.
The switches connected outside of the region exchange CIST information. By having devices look at the region identifiers, MSTP discovers the logical boundary of a region: