H3C Technologies H3C S7500E Series Switches - Manual (Page 185)

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automatically back to the MSTP (or RSTP) mode, but will remain working in the STP-compatible mode
under the following circumstances:
The device running STP is shut down or removed.
The device running STP migrates to the MSTP (or RSTP) mode.
By then, you can perform an mCheck operation to force the port to migrate to the MSTP (or RSTP)
mode.
You can perform mCheck on a port through the following two approaches, which lead to the same
result.
Performing mCheck globally
Follow these steps to perform global mCheck:
To do... Use the command... Remarks
Enter system view system-view —
Perform mCheck stp mcheck Required
Performing mCheck in interface view
Follow these steps to perform mCheck in interface view:
To do... Use the command... Remarks
Enter system view system-view —
Enter Ethernet interface view, or Layer 2
aggregate interface view
interface interface-type
interface-number
—
Perform mCheck stp mcheck Required
An mCheck operation takes effect on a device only when MSTP operates in RSTP or MSTP mode.
Configuring Digest Snooping
As defined in IEEE 802.1s, interconnected devices are in the same region only when the MST
region-related configurations (domain name, revision level, VLAN-to-instance mappings) on them are
identical. An MSTP-enabled device identifies devices in the same MST region by checking the
configuration ID in BPDU packets. The configuration ID includes the region name, revision level,
configuration digest that is in 16-byte length and is the result calculated via the HMAC-MD5 algorithm
based on VLAN-to-instance mappings.
Since MSTP implementations vary with vendors, the configuration digests calculated using private
keys is different; hence different vendors’ devices in the same MST region can not communicate with
each other.