3Com 4200G 12-Port Configuration Manual page 135

Root Bridge/Secondary
Root Bridge
Configuration
Admin configuration
Format selector
Region name
Revision level
Instance Vlans Mapped
0 11 to 19, 31 to 4094
1 1 to 10
2 20 to 30
MSTP can automatically choose a switch as a root bridge. You can also manually
specify the current switch as a root bridge by using the corresponding commands.
Root bridge configuration
Table 86 Specify the current switch as the root bridge of a specified spanning tree
Operation Command
Enter system view system-view
Specify the current stp [ instance instance-id ] root
switch as the root primary [ bridge-diameter
bridge of a specified bridgenumber ] [ hello-time
spanning tree centi-seconds ]
Secondary root bridge configuration
Table 87 Specify the current switch as the secondary root bridge of a specified spanning tree
Operation Command
Enter system view system-view
Specify the current stp [ instance instance-id ] root
switch as the secondary [ bridge-diameter
secondary root bridge bridgenumber ] [ hello-time
of a specified spanning centi-seconds ]
tree
Using the stp root primary/stp root secondary command, you can specify a switch
as the root bridge or the secondary root bridge of the spanning tree instance
identified by the instance-id argument. If the value of the instance-id argument is set
to 0, the stp root primary/stp root secondary command specify the current switch
as the root bridge or the secondary root bridge of the CIST.
A switch can play different roles in different spanning tree instances. That is, it can be
the root bridges in a spanning tree instance and be a secondary root bridge in
another spanning tree instance at the same time. But in one spanning tree instance, a
switch cannot be the root bridge and the secondary root bridge simultaneously.
When the root bridge fails or is turned off, the secondary root bridge becomes the
root bridge if no new root bridge is configured. If you configure multiple secondary
root bridges for a spanning tree instance, the one with the least MAC address
replaces the root bridge when the latter fails.
You can specify the network diameter and the Hello time parameters while
configuring a root bridge/secondary root bridge. Refer to "Network Diameter
Configuration" and "MSTP Time-related Configuration" for information about the
network diameter parameter and the Hello time parameter.
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Root Bridge Configuration 121
Description
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Required
Description
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Required