28.8.2 Configuring Multiple Spanning Tree

(1) Configuring Multiple Spanning Tree

Points to note

When the Spanning Tree operating mode is set to Multiple Spanning Tree, PVST+ and Single Spanning Tree stop and then Multiple Spanning Tree operation starts.

Command examples

1. (config)# spanning-tree mode mst

   Enables Multiple Spanning Tree and starts CIST operation.

Notes

When the no spanning-tree mode command is used to delete operating mode settings for Multiple Spanning Tree, the default operating mode of pvst is used. In this case, PVST+ operation starts automatically on the port VLAN.

(2) Region, Instance Configuration

Points to note

MST regions require that all switches belonging to the same region have the same region name, revision number, and MST instance settings.

The instance number of an MST instance and the VLAN to which the instance belongs are set at the same time. To make the regions match, the Switch allows unset VLAN IDs to be set for the belonging instance. VLANs for which no belonging instance is specified automatically belong to the CIST (instance 0).

As many as 16 MST instances can be set, including the CIST (instance 0).

Command examples

1. (config)# spanning-tree mst configuration

   (config-mst)# name "REGION TOKYO"

   (config-mst)# revision 1

   Switches to the Multiple Spanning Tree configuration mode, and sets name (region name) and revision (revision number).

2. (config-mst)# instance 10 vlans 100-150

   (config-mst)# instance 20 vlans 200-250

   (config-mst)# instance 30 vlans 300-350

   Sets instances 10, 20, and 30, and sets the VLANs belonging to each instance. For instance 10, set VLAN 100~150, instance 20 to VLAN 200~250, instance 30 with a VLAN 300~350. Other VLANs that are not specified belong to the CIST (instance 0).