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Configuring the device priority
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.
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.
To configure the priority of a device in a specified MSTI:
Step
Enter system view.
1.
Configure the priority of
2.
the current device.
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 device that received it. This prevents devices beyond the reach of the maximum
hop from participate in spanning tree calculation, so the size of the MST region is limited.
Make this configuration on the root bridge only. All other devices in the MST region use the maximum
hop value set for the root bridge.
To configure the maximum number of hops of an MST region:
Step
Enter system view.
1.
Configure the maximum
2.
hops of the MST region.
Command
system-view
•
In STP/RSTP mode:
stp priority priority
•
In PVST mode:
stp vlan vlan-list priority priority
•
In MSTP mode:
stp [ instance instance-id ] priority
priority
Command
system-view
stp max-hops hops
68
Remarks
N/A
Use one of the
commands.
The default setting is
32768.
Remarks
N/A
20 by default.
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