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Digest Snooping 205
By default, MSTP is enabled on all the ports after it is enabled on the device.
Displaying and
Debugging MSTP
After you configure MSTP, execute the display command in all views to display
the running of the MSTP configuration, and to verify the effect of the
configuration. Execute the
reset command in user view to clear the statistics of
MSTP module. Use the
debugging command in user view to debug the MSTP
module
Digest Snooping According to IEEE 802.1s, two connected switches can communicate through
MSTIs (multiple spanning tree instances) in a MSTP (multiple spanning tree
protocol) domain only when they are configured with the same domain settings.
With MSTP employed, interconnected switches determine whether or not they are
in the same domain by checking the configuration IDs of the BPDUs between
them. (Configuration ID comprises information such as domain ID and
configuration digest.)
As some switches come with some proprietary protocols concerning STP
employed, they cannot communicate with other switches in MSTP domains even
both of these two types of switches are configured with the same domain
configuration settings.
This can be overcome by implementing digest snooping. Digest snooping enables
a switch to track and maintain configuration digests of other switches that are in
the same domain by examining their BPDUs and insert corresponding
configuration digests in its BPDUs destined for these switches, through which
switches of different type are capable of communicating with each other in a
MSTP domain.
Configuring Digest
Snooping
Configure digest snooping on a switch to enable it to communicate in MSTP
domains with other switches that are configured with some proprietary protocols
to calculate configuration digest through MSTI.
Table 216 Display and Debug MSTP
Operation Command
Show the configuration information about the
current port and the switch.
display stp instance instance-id
[ interface interface-list ] [
brief ]
Show the configuration information about the
region.
display stp region-configuration
Clear the MSTP statistics information. reset stp [ interface
interface-list ]
Enable/Disable MSTP (packet
receiving/transmitting, event, error)
debugging on the port.
[ undo ] debugging stp [ interface
interface-list ] { packet | event
}
Enable/Disable the global MSTP debugging. [ undo ] debugging stp {
global-event | global-error | all
}
Enable/Disable specified STI debugging [ undo ] debugging stp instance
instance-id