This article provides brief information and steps to resolve the issue when the nodes in UDT are disabled for Layer 3 polling under Node Properties.
UDT version 3.2.3 or earlier
This behavior is actually by design within UDT, up until UDT 3.2.4 where it was disabled. The reason for this is that Layer 3 polling on those nodes is either returning no ARP data or the polling job has failed several times due to failure to respond on the device or no support for the ARP data tables in SNMP. UDT disables the layer 3 polling in this event to cut down on the amount of unnecessary polling jobs UDT is doing to decrease polling impact.
In some cases however, this can be detrimental for layer 3 polling in UDT. Such cases would be when the devices are brought down for maintenance, network outages or any other occurrence that results in the node being inaccessible or reachable by UDT. The same design will not work in reverse in such a regard: the polling will remain disabled even in the event the node returns.
For more information on finding and setting Layer 3 polling, you can check here.
To prevent this functionality from occurring, you can upgrade to UDT 3.2.4 where it has been disabled.