What's the definition of a 'Primary Address'?

In runZero, a primary address is one that responded directly to a probe of some sort. Any address that responds as part of a runZero network scan will be used as a primary address.

In addition, addresses reported by other tools that directly probe the network (such as Tenable, Qualys, or Nexpose) are treated as primary addresses.

runZero also enumerates other addresses, but doesn't use them for asset merging or as a source of truth, since they were claimed by the device, but not directly measured. These are collected as secondary addresses.

In some cases the active network address can be used to validate addresses returned by SNMP. If that's the case, the addresses are promoted to primary address status.