The command snmp-server host 192.168.5.5 informs version 3 noauth CISCO will configure the host to authenticate a user by username and send clear text notifications. The receiver will then acknowledge receipt of the notification. The keyword informs indicates that an inform message type will be used. Unlike a trap, an inform message is acknowledged by the receiver.

The version 3 keyword indicates that version 3 is in use, which is the ONLY version that supports authentication and encryption. Finally, the noauth keyword specifies authentication by username only and no encryption.

The command snmp-server host 192.168.5.5 traps version 3 auth public configures the host to send traps rather than informs.

The command snmp-server host 192.168.5.5 informs version 2c public specifies version 2c, which only support community string-based authentication.

The command snmp-server host 192.168.5.5 informs version 3 authpriv public specifies the keyword authpriv, which indicates encryption will be used and authentication based on HMAC-MD5 or HMAC-SHA algorithms.