H3C S6850 Series Configuration Guide

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• Revision level.
• VLAN-to-instance mappings.
A spanning tree device identifies devices in the same MST region by determining the configuration
ID in BPDUs. 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.
Restrictions and guidelines
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.
• 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.
• To make Digest Snooping take effect, you must enable Digest Snooping both globally and on
associated ports. As a best practice, 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.
• As a best practice, enable Digest Snooping first and then enable the spanning tree feature. To
avoid traffic interruption, do not configure Digest Snooping when the network is already working
well.
Prerequisites
Before configuring Digest Snooping, you need to make sure your H3C device and the third-party
device both run spanning tree protocols properly.
Procedure
1. Enter system view.
system-view
2. Enter interface view.
interface interface-type interface-number
3. Enable Digest Snooping on the interface.
stp config-digest-snooping
By default, Digest Snooping is disabled on ports.
4. Return to system view.
quit
5. Enable Digest Snooping globally.
stp global config-digest-snooping

H3C S6850 Series Specifications

General

Brand	H3C
Model	S6850 Series
Category	Switch
Language	English