Configuring the Root Bridge 217
a device to a low value, you can specify the device as the root bridge of the
spanning tree. An MSTP-compliant device can have different priorities in different
MST instances.
Configuration procedure
Follow these steps to configure the priority of the current device:
c
CAUTION:
■ Upon specifying the current device as the root bridge or a secondary root
bridge, you cannot change the priority of the device.
■ 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.
Configuration example
# Set the device priority in MST instance 1 to 4096.
<Sysname> system-view
[Sysname] stp instance 1 priority 4096
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 setting configured on the regional root bridge will be used as
the maximum hops of the MST region.
The regional root bridge always sends a configuration BPDU with a hop count set
to the maximum value. When a switch receives this configuration BPDU, it
decrements the hop count by 1 and uses the new hop count as the remaining hop
count in the BPDUs it propagates. When the hop count of a BPDU reaches 0, it is
discarded by the device that received it. Thus, devices beyond the reach of the
maximum hop are unable to take part in spanning tree calculation, and thereby
the size of the MST region is confined.
When a device becomes the root bridge of the CIST or MSTI of an MST region, the
maximum hop in the configuration BPDUs generated by this device defines the
network diameter of the spanning tree to define how far the spanning tree can
reach in this MST region. All the devices other than the root bridge in the MST
region use the maximum hop value set for the root bridge.
Configuration procedure
Follow these steps to configure the maximum hops of the MST region:
To do… Use the command… Remarks
Enter system view system-view -
Configure the priority of the
current device
stp [ instance instance-id ]
priority priority
Optional
32768 by default
To do… Use the command… Remarks
Enter system view system-view -
Configure the maximum hops of the MST region stp max-hops hops Optional
20 by default
To Next Page
Loading...
