As of NPM 10.4 there is no way to filter nodes which stopped responding SNMP packets but still pingable. There should be a "Group By" category on "Manage Nodes" section to filter nodes whose polling method is SNMP but became unresponsive to SNMP.
We deal with this EVERY DAY!!!! We created an alert to let us know when volumes go into unknown status (meaning snmp quit). then we have to remove all the volumes and add the new ones, losing all the history....
In this case, are you restarting SNMP on your devices and the volumes are showing up as new?
I would suggest to create alert based on "LastpolledUtc" object present in Nodes table. Whenever the device does not poll for ex. 30 mins. Alert should trigger. This would resolve the issue.
Thanks,
Syed
