Specifying The Root Bridge Or A Secondary Root Bridge - H3C S5120-SI Series Operation Manual

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Specifying the Root Bridge or a Secondary Root Bridge

MSTP can determine the root bridge of a spanning tree through MSTP calculation. Alternatively, you
can specify the current device as the root bridge using the commands provided by the system.
Specifying the current device as the root bridge of a specific spanning tree
Follow these steps to specify the current device as the root bridge of a specific spanning tree:
To do...
Enter system view
Specify the current device as
the root bridge of a specific
spanning tree
Specifying the current device as a secondary root bridge of a specific spanning tree
Follow these steps to specify the current device as a secondary root bridge of a specific spanning tree:
To do...
Enter system view
Specify the current device as a
secondary root bridge of a
specific spanning tree
Note that:
After specifying the current device as the root bridge or a secondary root bridge, you cannot
change the priority of the device.
You can configure the current device as the root bridge or a secondary root bridge of an MSTI,
which is specified by instance instance-id in the command. If you set instance-id to 0, the current
device will be the root bridge or a secondary root bridge of the CIST.
The current device has independent roles in different MSTIs. It can act as the root bridge or a
secondary root bridge of one instance while it can also act as the root bridge or a secondary root
bridge of another MSTI. However, the same device cannot be the root bridge and a secondary root
bridge in the same MSTI at the same time.
There is one and 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.
You can specify multiple secondary root bridges for the same instance. Namely, you can specify
secondary root bridges for the same instance on two or more than two devices.
When the root bridge of an instance fails or is shut down, the secondary root bridge (if you have
specified one) can take over the role of the primary root bridge. However, if you specify a new
primary root bridge for the instance at this time, the secondary root bridge will not become the root
bridge. If you have specified multiple secondary root bridges for an instance, when the root bridge
Use the command...
system-view
stp [ instance instance-id ]
root primary
Use the command...
system-view
stp [ instance instance-id ]
root secondary
1-18
Remarks
—
Required
By default, a device does not
function as the root bridge.
Remarks
—
Required
By default, a device does not
function as a secondary root
bridge.