3Com Switch 4200G Configuration Guide

Digest Snooping Configuration 141
Digest Snooping
Configuration
Introduction According to IEEE 802.1s, two interconnected MSTP switches can interwork with
each other through MSTIs in an MST region only when the two switches have the
same MST region-related configuration. Interconnected MSTP 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 partners' switches adopt proprietary spanning tree protocols, they cannot
interwork with other switches in an MST region even if they are configured with the
same MST region-related settings as other switches in the MST region.
This problem can be overcome by implementing the digest snooping feature. If a port
on a S4200G series switch is connected to a partner'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 S4200G series switch
regards the partner's switch as in the same region; it records the configuration digests
carried in the BPDUs received from the partner's switch, and put them in the BPDUs
to be send to the partner's switch.. In this way, the S4200G series switches can
interwork with the partners' switches in the same MST region.
Digest Snooping
Configuration
Configure the digest snooping feature on a switch to enable it to interwork with
other switches that adopt proprietary protocols to calculate configuration digests in
the same MST region through MSTIs.
Prerequisites
The switch to be configured is connected to a partner's switch that adopts a
proprietary spanning tree protocol. The MSTP network operates normally.
Configuration procedure
■ The digest snooping feature is needed only when your S4200G series switch is
connected to partner's proprietary protocol-adopted switches.
■ To enable the digest snooping feature successfully, you must first enable it on all
the ports of your S4200G series switch that are connected to partner's proprietary
protocol-adopted switches and then enable it globally.
Table 118 Configure the digest snooping feature
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 the 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.
Verify the above
configuration
display current-configuration You can execute this command in
any view.