Configuring Multiple Spanning Tree

Mapping and Unmapping VLANs to MST Instances

Mapping and Unmapping VLANs to MST Instances

Caution When you change the VLAN-to-MSTI mapping, the system restarts MST.

Note You cannot disable an MSTI.

For two or more bridges to be in the same MST region, they must have the identical MST name,

VLAN-to-instance mapping, and MST revision number.

Procedure

 

Command or Action

Purpose

Step 1

switch# configure terminal

Enters configuration mode.

Step 2

switch(config)# spanning-tree mst

Enters MST configuration submode.

 

configuration

 

Step 3

switch(config-mst)# instance

Maps VLANs to an MST instance, as follows:

 

instance-id vlan vlan-range

 

For instance-idthe range is from 1 to 4094.

 

 

Instance 0 is reserved for the IST for each MST

 

 

region.

 

 

For vlan-rangethe range is from 1 to 4094.

 

 

When you map VLANs to an MSTI, the mapping is

 

 

incremental, and the VLANs specified in the

 

 

command are added to or removed from the VLANs

 

 

that were previously mapped.

Step 4

switch(config-mst)# no instance

Deletes the specified instance and returns the VLANs to

 

instance-id vlan vlan-range

the default MSTI, which is the CIST.

This example shows how to map VLAN 200 to MSTI 3:

switch# configure terminal

switch(config)# spanning-tree mst configuration switch(config-mst)# instance 3 vlan 200

Mapping Secondary VLANs to Same MSTI as Primary VLANs for Private VLANs

When you are working with private VLANs on the system, all secondary VLANs must be in the same MSTI and their associated primary VLAN.

 

Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)

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Cisco Systems N3KC3048TP1GE, N3KC3064TFAL3 Mapping and Unmapping VLANs to MST Instances, Default MSTI, which is the Cist