H3C S7500E Series Command Manual page 231

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Command Manual – MSTP

H3C S7500E Series Ethernet Switches

instance instance-id: Configures the device as a secondary root bridge in a particular

spanning tree instance. The effective range of instance-id is 0 to 31, with 0 representing

bridge-number: Network diameter of the spanning tree, in the range of 2 to 7 and

defaulting to 7.

centi-seconds: Hello time (in centiseconds) of the spanning tree, in the range of 100 to

Use the stp root secondary command to configure the device as a secondary root

Use the undo stp root command to restore the system default.

By default, a device is not a secondary root bridge.

If you do not provide instance instance-id, your configuration will take effect in the

CIST instance only.

You can configure one or more secondary root bridges for each spanning tree

instance. When the root bridge of an instance fails or is shut down, the secondary

root bridge can take over the role of the instance of the specified spanning tree

instance. If you specify more than one secondary root bridge, the secondary root

bridge with the lowest MAC address will become the root bridge.

When configuring a secondary root bridge, you can specify the network diameter

of the switched network and the hello time for the secondary root bridge, so that

the MSTP-compliant device automatically calculates the other two timers (forward

delay and max age) of the root bridge.

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.

If you set instance-id to 0, you are specifying the current device as the secondary

root bridge of the CIST.

Upon specifying the current device as the root bridge or a secondary root bridge,

you cannot change the priority of the device.

# Define the current device as the secondary root bridge of spanning tree instance 0

and set the network diameter to 5 and the hello time of the device to 300 centiseconds.

Chapter 1 MSTP Configuration Commands

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