Supermicro SSE-G2252 User Manual page 209

Chapter 9: Spanning Tree Algorithm
Figure 9-2. MSTP Region, Internal Spanning Tree, Multiple Spanning Tree
An MST Region consists of a group of interconnected bridges that have the An MST
Region consists of a group of interconnected bridges that have the same MST
Configuration Identifiers (including the Region Name, Revision Level and Configuration
Digest – see Section 9-6: "Configuring Multiple Spanning Trees" on page 9-19). An MST
Region may contain multiple MSTP Instances. An Internal Spanning Tree (IST) is used
to connect all the MSTP switches within an MST region. A Common Spanning Tree
(CST) interconnects all adjacent MST Regions, and acts as a virtual bridge node for
communications with STP or RSTP nodes in the global network.
Figure 9-3. Common Internal Spanning Tree, Common Spanning Tree, Internal
Spanning Tree
Region 1 Region 1
CIST CST
Region 4 Region 4
IST
Region 2 Region 3 Region 2 Region 3
MSTP connects all bridges and LAN segments with a single Common and Internal
Spanning Tree (CIST). The CIST is formed as a result of the running spanning tree
algorithm between switches that support the STP, RSTP, MSTP protocols.
9-3