Performing Mcheck; Performing Mcheck Globally; Performing Mcheck In Interface View; Configuring Digest Snooping - H3C S7500E-X Configuration Manual

Performing mCheck

The mCheck feature enables user intervention in the port status transition process.
When a port on an MSTP, RSTP, or PVST device connects to an STP device and receives STP
BPDUs, the port automatically transits to the STP mode. However, the port cannot automatically
transit back to the original mode when the following conditions exist:
•
The peer STP device is shut down or removed.
•
The port cannot detect the change.
To forcibly transit the port to operate in the original mode, you can perform an mCheck operation.
For example, 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, PVST, 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, PVST, or MSTP with Device C,
you must perform mCheck operations on the ports interconnecting Device B and Device C.

Performing mCheck globally

Step
Enter system view.
1.
Perform mCheck.
2.

Performing mCheck in interface view

Step
Enter system view.
1.
Enter Layer 2 Ethernet or
2.
aggregate interface view.
Perform mCheck.
3.

Configuring Digest Snooping

CAUTION:
Use caution with global Digest Snooping in the following situations:
• When you modify the VLAN-to-instance mappings.
• When you restore the default MST region configuration.
If the local device has different VLAN-to-instance mappings than its neighboring devices, loops or
traffic interruption will occur.
As defined in IEEE 802.1s, connected devices are in the same region only when they have the same
MST region-related configurations, including:
Command
system-view
stp global mcheck
Command
system-view
interface interface-type
interface-number
stp mcheck
88
Remarks
N/A
The mCheck operation takes
effect on devices operating in
MSTP, PVST, or RSTP mode.
Remarks
N/A
N/A
The mCheck operation takes
effect on devices operating in
MSTP, PVST, or RSTP mode.