Configuring Digest Snooping

	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.

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 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 HPE device and a third-party device in the same MST region, enable Digest Snooping on the HPE device port connecting them.