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614 CHAPTER 38: MSTP CONFIGURATION COMMANDS
Description Use the stp max-hops command to set the maximum hops of the MST region on
the device.
Use the
undo stp max-hops command to restore the maximum hops to the
default setting.
By default, the maximum hops of an MST region is 20.
In the CIST and MST instances, the maximum hops setting configured on the
regional root bridge determines the maximum network diameter supported by the
MST region. After a configuration BPDU leaves the root bridge, its hop count is
decremented by 1 whenever it passes a device. When its hop count reaches 0, it
will be discarded by the device that has received it. As a result, devices beyond the
maximum hop count are unable to take part in spanning tree computing, and
thereby the size of the MST region is limited.
When the current device becomes the root bridge of the CIST or an MSTI, the
maximum hops setting configured on the device becomes the network diameter
of that spanning tree and restricts the size of that spanning tree in the current
MST region.
Devices other than the root bridge in an MST region use the maximum hops
setting on the root bridge.
Examples # Set the maximum hops of the MST region to 35.
<Sysname> system-view
[Sysname] stp max-hops 35
stp mcheck
Syntax stp mcheck
View System view/Ethernet interface view
Parameters None
Description Use the
stp mcheck command to carry out the mCheck operation globally or on
a port.
In a switched network, if a port on the device running MSTP (or RSTP) connects to
a device running STP, this port will automatically migrate to the STP-compatible
mode. However, if the device running STP is removed, this will not be able to
migrate automatically to the MSTP (or RSTP) mode, but will remain working in the
STP-compatible mode. In this case, you can perform an mCheck operation to force
the port to migrate to the MSTP (or RSTP) mode.
Note that the stp mcheck command is meaningful only when the device works in
the MSTP (or RSTP) mode, not in the STP-compatible mode.
Related commands: stp mode.