This read-write integer runs a diagnostic test against the Ethernet modules built into the unit's microhubs, selecting which specific hub (1 through 4) to exercise, and reports back testPass or testFailed. It lets an administrator isolate a faulty port-expansion microhub without swapping hardware, by testing each hub segment individually. For instance, if devices plugged into the third microhub segment are unreachable, the admin sets netioTest to testHub3(5) and checks the resulting value to see whether that specific hub reports testFailed.