ZyXEL Communications ES-2024 Series, User Manual, Page: 111 / 282

Chapter 13 Spanning Tree Protocol
ES-2024 Series User’s Guide
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13.1.4.3 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 56 MSTIs in Different Regions
13.1.4.4 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 57 MSTP and Legacy RSTP Network Example
13.2 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 .