If the only piece of information available is the NBP name, then an NBP lookup should be performed to turn that name into a DDP address. However, if there is a piece of stale information, it can be used as a hint to perform an NBP confirm (which sends a unicast to the network address which is presumed to be the target of the name lookup) to see if the stale information is, in fact, still valid.
An NBP name to DDP address mapping can also be confirmed implicitly using only SNMP transactions. For example, an SNMPv2 entity acting in a manager role issuing a retrieval operation could also retrieve the relevant objects from the NBP group  for the SNMPv2 entity acting in an agent role. This information can then be correlated with the source DDP address of the response.