H3C Technologies H3C S10500 Series Switches - Manual (Page 91)

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To do... Use the command... Remarks
Enter system view system-view —
Configure the current device as a secondary
root bridge (in STP/RSTP mode)
stp root secondary
Configure the current device as a secondary
root bridge (in PVST mode)
stp vlan vlan-list root secondary
Configure the current device as a secondary
root bridge (in MSTP mode) stp [ instance instance-id ] root
secondary
Required
Use any command.
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 numeric 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 (in STP/RSTP mode)
stp priority priority
Configure the priority of the current
device (in PVST mode)
stp vlan vlan-list priority priority
Configure the priority of the current
device (in MSTP mode) stp [ instance instance-id ] priority
priority
Required
Use any command.
32768 by default.
CAUTION:
•
You cannot change the priority of a device after it is configured as the root bridge or as a secondary root
bridge.
• During root bridge selection, if all devices in a spanning tree have the same priority, the one with the
lowest MAC address will be selected as the root bridge of the spanning tree.
Configuring the maximum hops of an MST region
By setting the maximum hops of an MST region, you can restrict the region size. The maximum hops
configured on the regional root bridge will be used as the maximum hops of the MST region.
Configuration BPDUs sent by the regional root bridge always have a hop count set to the maximum value.
When a device receives this configuration BPDU, it decrements the hop count by 1, and uses the new hop
count in the BPDUs that it propagates. When the hop count of a BPDU reaches 0, it is discarded by the