ZyXEL Communications 4528F, 4728F, XGS-4526 13.1.5.4 Common and Internal Spanning Tree (CIST)

Chapter 13 Spanning Tree Protocol

The following figure shows an example where there are two MST regions. Regions 1 and 2 have 2 spanning tree instances.

Figure 59 MSTIs in Different Regions

13.1.5.4 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 60 MSTP and Legacy RSTP Network Example

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	XGS-4526/4528F/4728F User’s Guide