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Chapter 11 Spanning Tree Protocol
ES-2048 User’s Guide
105
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 46 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 47 MSTP and Legacy RSTP Network Example
11.2 Spanning Tree Protocol Status Screen
The Spanning Tree Protocol status screen changes depending on what standard you choose to
implement on your network. Click Advanced Application > Spanning Tree Protocol to see
the screen as shown.