Mst Instance - ZyXEL Communications GS2210-8 User Manual

• VLAN- t o- MST I nst ance m apping

13.10.3 MST Instance

An MST I nst ance ( MSTI ) is a spanning t ree inst ance. VLANs can be configured t o run on a specific
MSTI . Each creat ed MSTI is ident ified by a unique num ber ( known as an MST I D) known int ernally
t o a region. Thus an MSTI does not span across MST regions.
The following figure shows an exam ple where t here are t wo MST regions. Regions 1 and 2 have 2
spanning t ree inst ances.
Figure 104 MSTI s in Different Regions
13.10.4 Common and Internal Spanning Tree (CIST)
A CI ST represent s t he connect ivit y of t he ent ire net work and it is equivalent t o a spanning t ree in
an STP/ RSTP . The CI ST is t he default MST inst ance ( MSTI D 0) . Any VLANs t hat are not m em bers of
an MST inst ance are m em bers of t he CI ST. I n an MSTP- enabled net work, t here is only one CI ST
t hat runs bet ween MST regions and single spanning t ree devices. A net work m ay cont ain m ult iple
MST regions and ot her net work segm ent s running RSTP .
Figure 105 MSTP and Legacy RSTP Net work Exam ple
Chapter 13 Spanning Tree Protocol
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