3Com MSR 30, MSR 50 manual Stp mcheck, Syntax stp mcheck

614CHAPTER 38: MSTP CONFIGURATION COMMANDS

Description Use the stp max-hopscommand to set the maximum hops of the MST region on the device.

Use the undo stp max-hopscommand 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.