Configuring Digest Snooping 177
Configuring Digest
Snooping
Introduction According to IEEE802.1s, 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 a Switch 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 other
manufacturer’s switch. In this way, the Switch 4210 can communicate with
another manufacturer’s switches in the same MST region.
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CAUTION: 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
Tab le 135 Configure digest snooping
Operation Command Description
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.
Return to system view quit -
Enable the digest snooping
feature globally
stp config-digest-snooping Required
The digest snooping feature is
disabled globally by default.
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