3com S7906E Manuel De Montage

 

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By then, you can perform an mCheck operation to force the port to migrate to the MSTP (or RSTP) 
mode. 

You can perform mCheck on a port through the following two approaches, which lead to the same 
result. 

Follow these steps to perform global mCheck: 

Enter system view 

 

— 

Perform mCheck 

 

Required 

 

Follow these steps to perform mCheck in interface view: 

Enter system view 

 

— 

Enter Ethernet interface view, or Layer 
2 aggregate interface view 

interface interface-type 
interface-number 

— 

Perform mCheck 

 

Required 

 

An mCheck operation takes effect on a device only when MSTP operates in RSTP or MSTP mode. 

 

As defined in IEEE 802.1s, interconnected devices are in the same region only when the MST 
region-related configurations (domain name, revision level, VLAN-to-instance mappings) on them are 
identical. An MSTP-enabled device identifies devices in the same MST region by checking the 
configuration ID in BPDU packets. The configuration ID includes the region name, revision level, 
configuration digest that is in 16-byte length and is the result calculated via the HMAC-MD5 algorithm 
based on VLAN-to-instance mappings. 

Since MSTP implementations vary with vendors, the configuration digests calculated using private keys 
is different; hence different vendors’ devices in the same MST region can not communicate with each 
other. 

Enabling the Digest Snooping feature on the port connecting the local device to a third-party device in 
the same MST region can make the two devices communicate with each other.