H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 68)

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A spanning tree can have one root bridge only. If two or more devices are selected as the root bridge in
a spanning tree at the same time, the device with the lowest MAC address wins out.
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 then, 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 fails, the secondary root
bridge with the lowest MAC address is selected as the new root bridge.
Configuring the current device as the root bridge of a specific spanning tree
Follow these steps to configure the current device as the root bridge of a specific spanning tree:
To do... Use the command... Remarks
Enter system view system-view —
Configure the current device as the
root bridge stp [ instance instance-id ] root
primary
Required
By default, a device does not
function as the root bridge.
Configuring the current device as a secondary root bridge of a specific spanning tree
Follow these steps to configure the current device as a secondary root bridge of a specific spanning tree:
To do... Use the command... Remarks
Enter system view system-view —
Configure the current device as a
secondary root bridge stp [ instance instance-id ] root
secondary
Required
By default, a device does not function
as a secondary root bridge.
NOTE:
•
You can specify one root bridge for each spanning tree, regardless of the device priority settings. Once
you specify a device as the root bridge or a secondary root bridge, you cannot change its priority.
• You can configure the current device as the root bridge by setting the device priority to 0. For the device
priority configuration, see “
Configuring the device priority .”
Configuring the device priority
Device priority is a factor in spanning tree calculation. The priority of a device determines whether the
device can be elected as the root bridge of a spanning tree. A lower value indicates a higher priority.
You can set the priority of a device to a low value to specify the device as the root bridge of the spanning
tree. A spanning tree device can have different priorities in different MSTIs.
Follow these steps to configure the priority of a device in a specified MSTI:
To do... Use the command... Remarks
Enter system view system-view —
Configure the priority of the current
device stp [ instance instance-id ] priority
priority Required
32768 by default.