Chapter 11 Spanning Tree Protocol

11.1.4.3 MST Instance

An MST Instance (MSTI) is a spanning tree instance. VLANs can be configured to run on a specific MSTI. Each created MSTI is identified by a unique number (known as an MST ID) known internally to a region. Thus an MSTI does not span across MST regions.

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

Figure 42 MSTIs in Different Regions

11.1.4.4 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 43 MSTP and Legacy RSTP Network Example

11.2 Spanning Tree Configuration Screen

Use this screen to select the STP mode for the Switch. To open this screen, click Advanced Application > Spanning Tree Protocol > Configuration.

 

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ES-2024 Series User’s Guide