vlan-mapping modulo

Function

The vlan-mapping modulo command configures VLAN-to-instance mapping based on a default algorithm.

The undo vlan-mapping modulo command restores the default mapping.

By default, all VLANs are mapped to Common and Internal Spanning Tree (CIST), namely, instance 0.

Format

vlan-mapping modulo modulo

undo vlan-mapping modulo

Parameters

Parameter	Description	Value
modulo	Specifies a module value.	The value is an integer ranging from 1 to 48.

Parameter

Description

Value

modulo

Specifies a module value.

The value is an integer ranging from 1 to 48.

Views

MSTP process region view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
mstp	write

Usage Guidelines

Usage Scenario

Multiple Spanning Tree Protocol (MSTP) divides a switching network into multiple regions, each of which has independent Multiple Spanning Trees. Each spanning tree is called a Multiple Spanning Tree instance (MSTI), and each region is called a Multiple Spanning Tree (MST) region.

Two devices belong to the same MST region only when their following configurations are the same:

MST region name
Mappings between MSTIs and VLANs
MST region revision level
To configure VLAN-to-instance mapping based on a default algorithm, run the vlan-mapping modulo command.

Precautions

The instance command is recommended because VLAN-to-instance mapping based on the algorithm cannot meet actual mapping requirements.

In the vlan-mapping modulo command, a VLAN is mapped to an instance based on this formula: Instance ID = MOD (VLAN ID-1)/Modulo value + 1. In the formula, MOD (VLAN ID-1)/Modulo value means the remainder of (VLAN ID-1) divided by the modulo value. For example, if the modulo is 16, VLAN 1 is mapped to MSTI 1, VLAN 2 to MSTI 2, VLAN 16 to MSTI 16, and VLAN 17 to MSTI 1.

Example

# Map all VLANs to spanning tree instances modulo 16.

<HUAWEI> system-view
[~HUAWEI] stp process 1
[~HUAWEI-mst-process-1] stp region-configuration
[~HUAWEI-mst-process-1-region] vlan-mapping modulo 16