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Configuring Digest Snooping
Introduction
According to IEEE 802.1s, two interconnected switches can communicate with each other through
MSTIs in an MST region only when the two switches have the same MST region-related configuration.
Interconnected MSTP-enabled switches determine whether or not they are in the same MST region by
checking the configuration IDs of the BPDUs between them (A configuration ID contains information
such as region ID and configuration digest).
As some other manufacturers' switches adopt proprietary spanning tree protocols, they cannot
communicate with the other switches in an MST region even if they are configured with the same MST
region-related settings as the other switches in the MST region.
This problem can be overcome by implementing the digest snooping feature. If a port on an 3Com
switches 4210 is connected to another manufacturer's switch that has the same MST region-related
configuration as its own but adopts a proprietary spanning tree protocol, you can enable digest
snooping on the port. Then the switch 4210 regards another manufacturer's switch as in the same
region; it records the configuration digests carried in the BPDUs received from another manufacturer's
switch, and put them in the BPDUs to be sent to the another manufacturer's switch. In this way, the
switch 4210 can communicate with another manufacturer’s switches in the same MST region.
The digest snooping function is not applicable to edge ports.
Configuring Digest Snooping
Configure the digest snooping feature on a switch to enable it to communicate with other switches
adopting proprietary protocols to calculate configuration digests in the same MST region through
MSTIs.
Configuration prerequisites
The switch to be configured is connected to another manufacturer's switch adopting a proprietary
spanning tree protocol. MSTP and the network operate normally.
Configuration procedure
Follow these steps to configure digest snooping:
To do... Use the command... Remarks
Enter system view
system-view
—
Enter Ethernet port view
interface interface-type
interface-number
—
Enable the digest snooping
feature
stp config-digest-snooping
Required
The digest snooping feature is
disabled on a port by default.
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