ZyXEL Communications XGS2210-28 - Common and Internal Spanning Tree (CIST)

Chapter 13 Spanning Tree Protocol
XGS2210 Series User’s Guide
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The following figure shows an example where there are two MST regions. Regions 1 and 2 have 2
spanning tree instances.
Figure 130 MSTIs in Different Regions
13.10.4 Common and Internal Spanning Tree (CIST)
A CIST represents the connectivity of the entire network and it is equivalent to a spanning tree in an STP/
RSTP. The CIST is the default MST instance (MSTID 0). Any VLANs that are not members of an MST instance
are members of the CIST. In an MSTP-enabled network, there is only one CIST that runs between MST
regions and single spanning tree devices. A network may contain multiple MST regions and other
network segments running RSTP.
Figure 131 MSTP and Legacy RSTP Network Example