H3C S6850 Series, Configuration Manual

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Configuring the device priority
About device priority
Device priority is a factor in calculating the spanning tree. 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 spanning
trees.
During root bridge selection, if all devices in a spanning tree have the same priority, the one with the
lowest MAC address is selected. You cannot change the priority of a device after it is configured as
the root bridge or as a secondary root bridge.
Procedure
1.
Enter system view.
system-view
2.
Configure the priority of the device.
{
In STP/RSTP mode:
stp priority priority
{
In PVST mode:
stp vlan vlan-id-list priority priority
{
In MSTP mode:
stp [ instance instance-list ] priority priority
The default setting is 32768.
Configuring the maximum hops of an MST region
About the maximum hops of an MST region
Restrict the region size by setting the maximum hops of an MST region. The hop limit configured on
the regional root bridge is used as the hop limit for 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 one, and
uses the new hop count in the BPDUs that it propagates. When the hop count of a BPDU reaches
zero, it is discarded by the device that received it. Devices beyond the reach of the maximum hops
can no longer participate in spanning tree calculations, so the size of the MST region is limited.
Restrictions and guidelines
Make this configuration only on the root bridge. All other devices in the MST region use the maximum
hop value set for the root bridge.
You can configure the maximum hops of an MST region based on the STP network size. As a best
practice, set the maximum hops to a value that is greater than the maximum hops of each edge
device to the root bridge.
Procedure
1.
Enter system view.
system-view
2.
Configure the maximum hops of the MST region.
stp max-hops hops
The default setting is 20.