How to make Digi Transport WR21 to send login and other enterprise traps

Digi Trasport WR21 has been configured for SNMPv3. SNMP get and set can be done. But no traps are sent by WR21 on bootup, login or ethernet disconnection, etc… Surprisingly the mib2 item snmpEnableAuthentraps is not writable

refer to the App note

http://ftp1.digi.com/support/utilities/QN_017_MIB_file_creation-updated.pdf