ZyXEL MGS-3712F User Guide - Page 130

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 69 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 130 MGS-3712/MGS-3712F User's Guide