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Performing mcheck, Performing mcheck globally, Performing mcheck in interface view – H3C Technologies H3C S12500-X Series Switches User Manual

Page 99: Calculation process of the stp algorithm

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Step Command

Remarks

4.

(Optional.) Enable the

spanning tree feature for the
port.

stp enable

By default, the spanning tree
feature is enabled on all ports.

Performing mCheck

The mCheck feature enables user intervention in the port status transition process.
If a port on a device that is running MSTP or RSTP connects to an STP device, this port automatically
transits to STP mode when the port receives STP BPDUs. However, if the peer STP device is shut down or

removed and the local device cannot detect the change, the local device cannot automatically transit

back to the original mode. To forcibly transit the port to operate in the original mode, you can perform

an mCheck operation.
Suppose a scenario where Device A, Device B, and Device C are connected in sequence. Device A runs

STP, Device B does not run any spanning tree protocol, and Device C runs RSTP or MSTP. In this case,

when Device C receives an STP BPDU transparently transmitted by Device B, the receiving port transits to

the STP mode. If you configure Device B to run RSTP or MSTP with Device C, you must perform mCheck

operations on the ports interconnecting Device B and Device C.
The following methods for performing mCheck produce the same result.

Performing mCheck globally

Step Command

1.

Enter system view.

system-view

2.

Perform mCheck.

stp global mcheck

Performing mCheck in interface view

Step Command

1.

Enter system view.

system-view

2.

Enter Layer 2 Ethernet or aggregate interface
view.

interface interface-type interface-number

3.

Perform mCheck.

stp mcheck

NOTE:

An mCheck operation takes effect on a device that operates in MSTP or RSTP mode.

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