AirLive SNMP-GSH2402 - Manual (Page 115)

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M Check:
Migration Check. It forces the port sending out an RSTP BPDU instead
of a legacy STP BPDU at the next transmission. The only benefit of this
operation is to make the port quickly get back to act as an RSTP port.
Click <M Check> button to send a RSTP BPDU from the port you
specified.
Fig. 3-48