3Com 8807 Command Reference Manual page 186

184 C 13: MSTP C C
HAPTER ONFIGURATION OMMANDS
stp instance root Syntax
primary
stp [ instance instance-id ] root primary [ bridge-diameter bridgenum [
hello-time centi-senconds ] ]
undo stp [ instance instance-id ] root
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Parameter
instance-id: Specifies the spanning tree instance ID, ranging from 0 to 48. Specify
it as 0 to configure the root bridge of CIST.
root primary: Configures the current switch as the primary root of the specified
MSTI.
bridge-diameter bridgenum: Specifies the network diameter of the spanning
tree, ranging from 2 to 7.
hello-time centi-senconds: Specifies the Hello Time of the spanning tree, which is
in the range from 100 to 1000 and measured in centiseconds.
Description
Use the stp root primary command to configure the current switch as the
primary root of the specified MSTI.
Use the undo stp root command to cancel the current switch for the primary root
of the designated MSTI.
If you execute these commands without using the instance instance-id option,
your configuration takes effect only on the CIST instance.
When you set the instance-id parameter to 0, its following parameter setting takes
effect.
By default, the switch does not server as a root bridge.
You can specify one root bridge for each MSTI regardless of the switch priority.
When setting a root bridge, you can use this command to specify the switching
network diameter and determine the three time parameters (Hello time, Forward
Delay and Max Age). Because the switch calculates inaccurate Hello time value,
you can specify the switching network diameter and the Hello Time for the root
bridge, and thus determine other two parameter values for the root bridge. In
general, you are recommended to determine the other two time parameter values
by setting the network diameter.
c
CAUTION: In a switching network, you can configure only one root bridge for
each MSTI and one or more secondary switches. Do not configure more than one
root bridge for an MSTI at the same time. Otherwise, the calculation result will be
unpredictable.