H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 88)

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Performing mCheck
If a port on a device running MSTP or RSTP connects to an STP device, this port automatically transitions
to the STP-compatible mode. However, it cannot automatically transition back to the original mode when:
• The STP device is shut down or removed.
• The STP device transitions to the MSTP or RSTP mode.
To forcibly transition the port to operate in the original mode, you can perform an mCheck operation.
You can perform mCheck on a port through the following two approaches, which lead to the same result.
Performing mCheck globally
Step Command
1. Enter system view. system-view
2. Perform mCheck. stp mcheck
Performing mCheck in interface view
Step Command
1. Enter system view. system-view
2. Enter Ethernet 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.
Configuring Digest Snooping
As defined in IEEE 802.1s, interconnected devices are in the same region only when the MST
region-related configurations (region name, revision level, VLAN-to-instance mappings) on them are
identical. A spanning tree 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.
Spanning tree implementations vary with vendors, and the configuration digests calculated using private
keys is different. As a result, devices of different vendors in the same MST region cannot communicate
with each other.
To enable communication between an H3C device and a third-party device, enable the Digest Snooping
feature on the port connecting the H3C device to the third-party device in the same MST region.
NOTE:
Before enabling Digest Snooping, be sure that associated devices of different vendors are connected and
run spanning tree protocols.