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The figure shows there are 2 VLANs/MSTP Instances and each instance has its Root and
forwarding paths.
A Common Spanning Tree (CST) interconnects all adjuacent MST regions and acts as a
virtual bridge node for communications with STP or RSTP nodes in the global network.
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.
The figure shows the CST large network. In this network, a Region may has different
instances and its own forwarding path and table, however, it acts as a single Brige of CST.
To configure the MSTP setting, the STP Mode of the STP Configuration page should be
changed to MSTP mode first.