3Com Switch 7750 SeriesCommand Reference Guide – MSTP Chapter 1 MSTP Configuration Commands1-17Parameterinterface-list: Ethernet port list. You can specify multiple Ethernet ports by providing thisargument in the format of interface-list ={ interface-type interface-number [ tointerface-type interface-number ] } &<1-10>, where &<1-10> means that you canprovide up to 10 port indexes/port index ranges for this argument.DescriptionUse the stp interface config-digest-snooping command to enable the digestsnooping feature.Use the undo stp interface config-digest-snooping command to disable the digestsnooping feature.By default, the digest snooping feature is disabled.According to IEEE 802.1s, two interconnected MSTP switches can interwork with eachother through MSTIs in an MST region only when the two switches have the same MSTregion-related configuration. Interconnected MSTP switches determine whether or notthey are in the same MST region by checking the configuration IDs of the BPDUsbetween them. (A configuration ID contains information such as region ID andconfiguration digest.)As some partners' switches adopt proprietary spanning tree protocols, they cannotinterwork with other switches in an MST region even if they are configured with thesame MST region-related settings as other switches in the MST region.This problem can be overcome by implementing the digest snooping feature. If a porton an Switch 7750 series switch is connected to a partner's switch that has the sameMST 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 thepartner's switch as in the same region; it records the configuration digests carried in theBPDUs received from the partner's switch, and put them in the BPDUs to be send to thepartner's switch. In this way, the Switch 7750 switches can interwork with the partners'switches in the same MST region.
