Don't know if anyone else has encountered this but here goes.
In NPM we have this handy little pie chart. So when attempting to fix the undefined nodes, I check the snmp settings on the server in question and find that the physical as well as the datalink and subnetworks checkboxes have been cleared.
So I re-check them, restart the snmp service and proceed into NPM.
I list the resources but the hardware check box is missing from the list.
I have tried re-adding the pollers but it does me no good.
Anyone have any ideas how to resolve this issue?