3Com 7750 Series Command Reference Manual page 267

3Com Switch 7750 Series
Command Reference Guide – MSTP
Parameter
interface-list: Ethernet port list. You can specify multiple Ethernet ports by providing this
argument in the format of interface-list ={ interface-type interface-number [ to
interface-type interface-number ] } &<1-10>, where &<1-10> means that you can
provide up to 10 port indexes/port index ranges for this argument.
Description
Use the stp interface config-digest-snooping command to enable the digest
snooping feature.
Use the undo stp interface config-digest-snooping command to disable the digest
snooping feature.
By default, the digest snooping feature is disabled.
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 an Switch 7750 series switch is connected to a partner's switch that has the same
MST region-related settings as its own but adopts a proprietary spanning tree protocol,
you can enable digest snooping on the port. Then the Switch 7750 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 Switch 7750 switches can interwork with the partners'
switches in the same MST region.
Chapter 1 MSTP Configuration Commands
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