NetFlow is a Cisco IOS application that provides statistics on packets flowing through routers. NetFlow is primarily used for network accounting and identifies flows of packets coming in and going out of an interface. The beauty of NetFlow is that it does not involve any additional protocol setup between network devices or hosts. NetFlow is completely transparent to the existing network devices, hosts, and applications. NetFlow can be enabled individually on some network devices like routers and switches, without having to enable it on all devices in the network.