SMC Networks TigerAccess SMC7816M - Manual (Page 303)

12-3
maintain connectivity among each of the assigned VLAN groups. MSTP
then builds a Internal Spanning Tree (IST) for the Region containing all
commonly configured MSTP bridges.
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 “Configuring Multiple
Spanning Trees” on page 12-22). 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.