Mst Instance - ZyXEL Communications MGS-3712/MES-3728 User Manual

Chapter 13 Spanning Tree Protocol
Devices that belong to the same MST region are configured to have the same
MSTP configuration identification settings. These include the following parameters:
• Name of the MST region
• Revision level as the unique number for the MST region
• VLAN-to-MST Instance mapping

13.1.5.3 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 67 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
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MES-3728 User's Guide