3Com Switch 8800 Family Configuration Guide

134 CHAPTER 17: MSTP REGION-CONFIGURATION
By default, the MST region name is the switch MAC address, all the VLANs in the
MST region are mapped to the STI 0, and the MSTP region revision level is 0. You
can restore the default settings of MST region, using the undo stp
region-configuration command in system view.
Configuring the mapping relationship between a VLAN list and a Spanning
Tree Instance
MSTP describes the mapping relationship between VLAN and Spanning Tree
instances through the VLAN mapping table. You can use this command to
configure the VLAN mapping table: each VLAN can be allocated to different
Spanning Tree instances according to your configuration.
You cannot map one VLAN to different instances. When you map a mapped VLAN
to a different MSTI, the previous mapping relationship will be automatically
cancelled.
The vlan-mapping modulo modulo command can specify a VLAN to each
Spanning Tree instance quickly. This command maps a VLAN to the Spanning Tree
instance whose ID is (VLAN ID-1) %modulo+1. (Note: (VLAN ID-1) %modulo is the
modulo operation for (VLAN ID-1). If the modulo operation is based on 16, VLAN
1 is mapped to MSTI 1, VLAN 2 is mapped to MSTI 2...VLAN 16 is mapped to MSTI
16, VLAN 17 is mapped to VLAN 17, and so on.)
Perform the following configurations in MST region view.
By default, all the VLAN lists are mapped to CIST, namely, Instance 0.
Activating the MST region configuration, and exit the MST region view
Perform the following configuration in MST region view.
Specifying the Switch as
a Primary or a Secondary
Root bridge
MSTP can determine the spanning tree root through calculation. You can also
specify the current switch as the root, using the command provided by the switch.
You can use the following commands to specify the current switch as the primary
or secondary root of the spanning tree.
Tabl e 106 Map all the VLAN lists to the specific Spanning Tree instances
Operation Command
Map all the VLAN lists to the specific Spanning
Tree instances uniformly through the modulo
operation
vlan-mapping modulo modulo
Restore the default mapping relationship
between VLAN lists and Spanning Tree
instances
undo vlan-mapping modulo
Tabl e 107 Activate the MST region configuration and exit the MST region view
Operation Command
Show the configuration information of the
MST region under revision
check region-configuration
Manually activate the MST region
configuration
active region-configuration
Exit MST region view quit