Command Manual – MSTP
H3C S7500E Series Ethernet Switches Chapter 1 MSTP Configuration Commands
1-31
centi-seconds: Hello time (in centiseconds) of the spanning tree, in the range of 100 to
1,000.
Description
Use the stp root primary command to configure the current device as the root bridge.
Use the undo stp root command to restore the system default.
By default, a device is not a root bridge.
Note that:
z If you do not provide instance instance-id, your configuration will take effect in the
CIST instance only.
z There is only one root bridge in effect in a spanning tree instance. If two or more
devices have been designated to be root bridges of the same spanning tree
instance, MSTP will select the device with the lowest MAC address as the root
bridge.
z You can specify a root bridge for each spanning tree instance without caring about
the device priority. After specifying the current device as the root bridge or a
secondary root bridge, you cannot change the priority of the device.
z When configuring a root bridge, you can use this command to specify the network
diameter of the switched network, so that the MSTP-compliant device
automatically calculates the three timers (hello time, forward delay and max age).
As the calculated hello time value is not the optimal value, you can specify a hello
time value by providing hello-time centi-seconds in the command, which will
override the hello time value calculated by the device based on the network
diameter. Generally, we recommend that you use the values of the other two
timers calculated by the device based on the specified network diameter.
z The configured network diameter and hello time settings are effective only for
spanning tree instance 0, namely the CIST. If you configure these two timers for
any other instance, your configuration can succeed, but they will not actually work.
Examples
# Define the current device as the root bridge of spanning tree instance 0 and set the
network diameter to 4 and the hello time of the device to 500 centiseconds.
<Sysname> system-view
[Sysname] stp instance 0 root primary bridge-diameter 4 hello-time 500
1.1.33 stp root secondary
Syntax
stp [ instance instance-id ] root secondary [ bridge-diameter bridge-number ]
[ hello-time centi-seconds ]
undo stp [ instance instance-id ] root
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