ABC Series are a bit different than the others in terms of clearing out default snmp configuration and I've found that the little nuances are tricky as well. Normally, when I start working with the C's, I clear out everything and then put in my own snmp v3 config:
clear snmp access ro security-model v1
clear snmp access ro security-model v2c
clear snmp access public security-model v1
clear snmp access public security-model v2c
clear snmp access public security-model usm
clear snmp group ro ro security-model v1
clear snmp group ro ro security-model v2c
clear snmp group public public security-model v1
clear snmp group public public security-model v2c
clear snmp user public
Then:
set snmp group
user security-model usm
set snmp access security-model usm privacy exact read All write All notify All nonvolatile set snmp user authentication md5 encryption des privacy That's it in a nutshell. You can change around your authentication algorithm and privacy encryption to match your nms.