Configuring Digest Snooping; Introduction - H3C S3100-52P Operation Manual

Operation Manual – MSTP
H3C S3100-52P Ethernet Switch

1.7 Configuring Digest Snooping

1.7.1 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 S3100-52P Ethernet switch 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
S3100-52P Ethernet switch 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 S3100-52P Ethernet switch can communicate
with another manufacturer's switches in the same MST region.
Caution:
The digest snooping function is not applicable to edge ports.
1.7.2 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.
I. 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.
II. Configuration procedure
Follow these steps to configure digest snooping:
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Chapter 1 MSTP Configuration