112
Step Command
2.
Enter Layer 2 Ethernet or aggregate 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 their 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 H3C device and a third-party device in the same MST region,
enable Digest Snooping on the H3C 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, so the VLAN-to-instance mappings must be the same on associated ports.
•
With Digest Snooping enabled globally, modify the VLAN-to-instance mappings or execute the
undo stp region-configuration
command to restore the default MST region configuration with
caution. If the local device has different VLAN-to-instance mappings than its neighboring devices,
loops or traffic interruption occurs.
•
To make Digest Snooping take effect, you must enable Digest Snooping both globally and on
associated ports. H3C recommends that you enable Digest Snooping on all associated ports first
and then enable it globally. This will make the configuration take effect on all configured ports and
reduce impact on the network.
•
To prevent loops, do not enable Digest Snooping on MST region edge ports.
•
H3C recommends that you enable Digest Snooping first and then the spanning tree feature. To
avoid traffic interruption, do not configure Digest Snooping when the network is already working
well.
