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AR500, AR510, and AR530 V200R007 CLI-based Configuration Guide - Ethernet Switching

This document describes the configuration of Ethernet services, including configuring transparent bridge, MAC table, link aggregation, VLANs, STP/RSTP/MSTP, and so on.The document provides the configuration procedures and configuration examples to illustrate the service configuration methods and application scenario.
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Configuring and Activating an MST Region

Configuring and Activating an MST Region


An MST region contains multiple switching devices and network segments. These switching devices are directly connected and have the same region name, same VLAN-to-instance mapping, and the same configuration revision number after MSTP is enabled. One switching network can have multiple MST regions. You can use MSTP commands to group multiple switching devices into one MST region.

Two switching devices belong to the same MST region when they have the same:
  • Name of the MST region

  • Mapping between VLANs and MSTIs

  • Revision level of the MST region

Perform the following steps on a switching device that needs to join an MST region.


  1. Run:


    The system view is displayed.

  2. Run:

    stp region-configuration

    The MST region view is displayed.

  3. Run:

    region-name name

    The name of an MST region is configured.

    By default, the MST region name is the MAC address of the management network interface on the MPU of the switching device.

  4. Perform either of the following steps to configure VLAN-to-instance mappings.

    • Run the instance instance-id vlan { vlan-id1 [ to vlan-id2 ] }&<1-10> command to configure VLAN-to-instance mappings.

    • Run the vlan-mapping modulo modulo command to enable VLAN-to-instance mapping assignment based on a default algorithm.

    By default, all VLANs in an MST region are mapped to MSTI 0.

    • The VLAN-to-instance mappings generated using the vlan-mapping modulo modulo commands cannot meet network requirements. It is recommended that you run the instance instance-id vlan { vlan-id1 [ to vlan-id2 ] }&<1-10> command to configure VLAN-to-instance mappings.

    • The vlan-mapping modulo specifies the formula (VLAN ID-1)%modulo+1. In the formula, (VLAN ID-1)%modulo means the remainder of (VLAN ID-1) divided by the value of modulo. This formula is used to map a VLAN to the corresponding MSTI. The calculation result of the formula is the ID of the mapping MSTI.

  5. (Optional) Run:

    revision-level level

    The MSTP revision number is set.

    By default, the MSTP revision number is 0.

    If the revision number of the MST region is not 0, this step is necessary.


    Changing MST region configurations (especially change of the VLAN mapping table) triggers spanning tree recalculation and causes route flapping. Therefore:

    • After configuring an MST region name, VLAN-to-instance mappings, and an MSTP revision number, run the check region-configuration command in the MST region view to verify the configuration. After confirming the region configurations, run the active region-configuration command to activate MST region configurations.
    • You are advised not to modify MST region parameters after the MST region is activated.

  6. Run:

    active region-configuration

    MST region configurations are activated so that the configured region name, VLAN-to-instance mappings, and revision number can take effect.

    If this step is not done, the preceding configurations cannot take effect.

    If you have changed MST region configurations on the switching device after MSTP starts, run the active region-configuration command to activate the MST region so that the changed configurations can take effect.

Updated: 2019-05-25

Document ID: EDOC1000097279

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