Configuring and Activating an MST Region
Context
An MST region contains multiple switches and network segments. These switches are directly connected and, after MSTP is enabled, have the same region name, VLAN-to-MSTI mapping, and configuration revision number. One switching network can have multiple MST regions. Running MSTP commands allows you to group multiple switches into one MST region.
Name of the MST region
Mapping between VLANs and MSTIs
Revision level of the MST region
Perform the following steps on a switch that needs to join an MST region.
Procedure
- Run:
system-viewThe system view is displayed.
- Run:
stp region-configurationThe MST region view is displayed.
- 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 switch.
- 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.
To configure the mapping between the spanning tree instance and MUX VLAN, you are advised to configure the principal VLAN, and subordinate group VLANs and subordinate separate VLANs of the MUX VLAN in the same protected instance. Otherwise, loops may occur.
- (Optional) Run:
revision-level level
The MSTP revision number is set.
By default, the MSTP revision number is 0.
MSTP is a standard protocol; therefore, the MSTP revision level of a device is 0 by default. If the revision level of some devices from a specified manufacturer is not 0, you must change the value to 0 to facilitate tree calculation in an MST region.
Changing MST region configurations (especially changes in the VLAN mapping table) triggers spanning tree recalculation and may cause route flapping. Therefore:
- After configuring an MST region name, VLAN-to-MSTI 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.
- Run:
active region-configurationMST region configurations are activated so that the configured region name, VLAN-to-MSTI mappings, and revision number can take effect.
The preceding configurations do not take effect until this command is run.
If MST region configurations on the switch change after MSTP starts, the active region-configuration command must be run before the changes take effect.
Before using the active region-configuration command to activate the modified MST region parameters, run the check region-configuration command to check whether parameters are correct. After the active region-configuration command is run, if a message that indicates an activation failure is displayed, reconfigure MSTP parameters.