Mapping VLANs to a MSTP Instance

The VLAN to MSTP Instance page enables you to map each VLAN to a Multiple Spanning Tree Instance (MSTI). For devices to be in the same region, they must have the same mapping of VLANs to MSTIs.

NOTE     The same MSTI can be mapped with more than one VLAN, but each VLAN can only have one MST Instance attached to it.

Configuration on this page (and all of the MSTP pages) applies if the system STP mode is MSTP.

Up to seven MST instances can be defined on Cisco Small Business 300 Series switches. Up to 16 MST instances can be defined on the Cisco 350 Series switches. For those VLANs that are not explicitly mapped to one of the MST instances, the switch automatically maps them to the CIST (Core and Internal Spanning Tree) instance. The CIST instance is MST instance 0.

To map VLANs to MST Instances:

  1. Click Spanning Tree > VLAN to MST Instance. The VLAN to MST Instance page displays.
  2. The VLAN to MST Instance page contains the following fields:

    • MST Instance ID--All MST instances are displayed.
    • VLANs--All VLANs belonging to the MST instance are displayed.
  3. To add a VLAN to an MST instance, select the MST instance, and click Edit. The Edit MST Instance to VLAN page displays.
  4. Enter the parameters.
    • MST Instance ID--Select the MST instance.
    • VLANs--Define the VLANs being mapped to this MST instance.
    • Action--Define whether to Add (map) or Remove the VLAN to/from the MST instance.
  5. Click Apply. The MSTP VLAN mappings are defined, and the Running Configuration file is updated..