3Com 5500-EI PWR Reference Manual page 264

View
System view
Parameters
instance-id: MSTI ID ranging from 0 to 16. The value of 0 refers to the CIST.
bridgenum: Network diameter of the specified spanning tree. This argument ranges from 2 to 7 and
defaults to 7.
centi-seconds: Hello time in centiseconds of the specified spanning tree. This argument ranges from
100 to 1,000 and defaults to 200.
Description
Use the stp root primary command to configure the current switch as the root bridge of a specified
MSTI.
Use the undo stp root command to cancel the current configuration.
By default, a switch is not configured as a root bridge.
If you do not specify the instance-id argument, these two commands apply to only the CIST.
You can specify the current switch as the root bridge of an MSTI regardless of the priority of the switch.
You can also specify the network diameter of the switched network by using the stp root primary
command. The switch will then figure out the following three time parameters: hello time, forward delay,
and max age. As the hello time figured out by the network diameter is not always the optimal one, you
can set it manually through the hello-time centi-seconds parameter. Generally, you are recommended
to obtain the forward delay and max age parameters through setting the network diameter.
You can configure only one root bridge for an MSTI and can configure one or more secondary root
bridges for an MSTI. Specifying multiple root bridges for an MSTI causes unpredictable spanning
tree calculation results.
Once a switch is configured as the root bridge or a secondary root bridge, its priority cannot be
modified.
Examples
# Configure the current switch as the root bridge of MSTI 1, set the network diameter of the switched
network to 4, and set the hello time to 500 centiseconds.
<Sysname> system-view
System View: return to User View with Ctrl+Z.
[Sysname] stp instance 1 root primary bridge-diameter 4 hello-time 500
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