3Com 10014298 manual Digest Snooping, Configuring Digest

Digest Snooping 205

By default, MSTP is enabled on all the ports after it is enabled on the device.

Displaying and After you configure MSTP, execute the display command in all views to display Debugging MSTP 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

Table 216 Display and Debug MSTP

Operation	Command
Show the configuration information about the	display stp instance instance-id
current port and the switch.	[ interface interface-list ] [
	brief ]
Show the configuration information about the	display stp region-configuration
region.
Clear the MSTP statistics information.	reset stp [ interface
	interface-list ]

Enable/Disable MSTP (packet receiving/transmitting, event, error) debugging on the port.

Enable/Disable the global MSTP debugging.

Enable/Disable specified STI debugging

[ undo ] debugging stp [ interface interface-list ] { packet event

}

[ undo ] debugging stp { global-event global-error all

}

[ undo ] debugging stp instance instance-id

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	Configure digest snooping on a switch to enable it to communicate in MSTP
Snooping	domains with other switches that are configured with some proprietary protocols
	to calculate configuration digest through MSTI.