This value lists which IPv4 header fields (for example source address, destination address, or port) the NetflowRecordDef uses as the flow-identifying key for IPv4 traffic. An administrator reviewing exported flow records needs to know ipv4keys to understand exactly how granular the IPv4 flow breakdown will be, since two packets that differ only in a field not included here get counted as the same flow. For example, a record definition whose ipv4keys omits the destination port would merge all traffic between two hosts into a single flow entry regardless of which application ports were involved.