R0106-HP MSR Router Series Layer 2 - LAN Switching Configuration Guide(V7)

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Configuration procedure
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 interface view.
interface interface-type interface-number
3. Perform mCheck.
stp mcheck
Configuring Digest Snooping
As defined in IEEE 802.1s, connected devices are in the same region only when they have the same MST
region-related configurations, including:
• Region name.
• Revision level.
• VLAN-to-instance mappings.
A spanning tree device identifies devices in the same MST region by determining the configuration ID in
BPDU packets. The configuration ID includes the region name, revision level, and configuration digest. It
is 16-byte long and is the result calculated through the HMAC-MD5 algorithm based on
VLAN-to-instance mappings.
Because spanning tree implementations vary by vendor, the configuration digests calculated through
private keys are different. The devices of different vendors in the same MST region cannot communicate
with each other.
To enable communication between an HP device and a third-party device in the same MST region,
enable Digest Snooping on the HP device port connecting them.
Configuration restrictions and guidelines
When you configure Digest Snooping, follow these guidelines:
• Before you enable Digest Snooping, make sure associated devices of different vendors are
connected and run spanning tree protocols.
• With Digest Snooping enabled, in-the-same-region verification does not require comparison of
configuration digest. The VLAN-to-instance mappings must be the same on associated ports.
• With Digest Snooping enabled globally, use caution when you modify the VLAN-to-instance
mappings or execute the undo stp region-configuration command to restore the default MST region
configuration. If the local device has different VLAN-to-instance mappings than its neighboring
devices, loops or traffic interruption occurs.