First go to iDRAC Settings > Services > SNMP Agent.

• Change you SNMP Community Name. (This is not used for SNMPv3)
• Enable SNMPv3.

Next go to iDRAC Settings > Users.

Edit the current user, or create a new user. Scroll down to SNMP V3 Settings.

• Change SNMP v3 to Enabled.
• Enable Passphrase.
• Set Authentication and Privacy Passphrases.
• Save.

Add your iDRAC to your monitoring software. You can verify everything works from a Linux machine that has the SNMP utils installed.

snmpwalk -v3 -a SHA1 -A "snmpv3userpass" -x AES -X "snmpv3userpass" -l authPriv -u root 192.168.1.100