H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 84)

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Configuring the root bridge or a secondary root
bridge
You can have MSTP determine the root bridge of a spanning tree through MSTP calculation, or you can
specify the current device as the root bridge or as a secondary root bridge.
A device has independent roles in different spanning trees. It can act as the root bridge in one spanning
tree and as a secondary root bridge in another. However, one device cannot be the root bridge and a
secondary root bridge in the same spanning tree.
A spanning tree can have only one root bridge. If two or more devices are selected as the root bridge at
the same time, the device with the lowest MAC address wins.
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 one that you specify, rather than the secondary root bridge, will
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.
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 current device as the root bridge of a specific
spanning tree
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure the current
device as the root
bridge.
• In STP/RSTP mode:
stp root primary
• In PVST mode:
stp vlan vlan-list root primary
• In MSTP mode:
stp [ instance instance-id ] root primary
Use one of the commands.
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
Step Command Remarks
1. Enter system view. system-view N/A