NRT grapher does not work with SNMPv3 and AuthNoPriv configured.
With AuthPriv NRT works as excepted.

Tested with Net-SNMP on debian (but also a problem on other devices).

To test this behaviour:

1. create AuthNoPriv and AuthPriv user

/etc/init.d/snmpd stop
net-snmp-config --create-snmpv3-user -ro -a SHA -A pw-authnp123 opennms
net-snmp-config --create-snmpv3-user -ro -a SHA -A pw-auth123 -x AES -X pw-priv123 opennms-ap
/etc/init.d/snmpd start

2. verify access

snmpwalk -v 3 -u opennms -n "" -l authNoPriv -a SHA -A pw-authnp123 localhost
snmpwalk -v 3 -u opennms-ap -n "" -l authPriv -a SHA -A pw-auth123 -x AES -X pw-priv123 localhost

3. change snmp-config.xml to the following

<snmp-config port="161" retry="3" timeout="3600" version="v3" auth-protocol="SHA" auth-passphrase="pw-authnp123" security-name="opennms" />

-> NRT grapher shows always NaN (or null in debug)

4. change snmp-config.xml to the following

<snmp-config port="161" retry="3" timeout="3600" version="v3" privacy-protocol="AES" privacy-passphrase="pw-priv123" auth-protocol="SHA" auth-passphrase="pw-auth123" security-name="opennms-ap" />

-> NRT grapher works as excepted