Net Inspector incorporates a NetFlow collector and analyzer module that receives NetFlow v5 and v9 protocol packets and sFlow v5 packets from source devices and provides aggregated statistics about IP traffic (network flows) on NetFlow/sFlow-enabled equipment (like the Cisco IOS devices).
NetFlow is a network protocol for collecting IP traffic information. NetFlow version 9 is documented in RFC 3954.
RFC 3954 defines (network) flow as follows:
A flow is defined as a unidirectional sequence of packets with some common properties that pass through a network device. These collected flows are exported to an external device, the NetFlow collector. Network flows are highly granular; for example, flow records include details such as IP addresses, packet and byte counts, timestamps, Type of Service (ToS), application ports, input and output interfaces, etc.
sFlow stands for "sampled flow" and is a method for sampling and exporting truncated packets, together with interface counters. Maintenance of the protocol is performed by the sFlow.org consortium. sFlow v5 (http://sflow.org/sflow_version_5.txt) is supported by Net Inspector.
NetFlow and sFlow monitoring provides insight into how the network is utilized in terms of applications that generate the most traffic (in bytes and packets), it lets you view which endpoints (IP addresses) are the source and destination of the heaviest traffic, what protocols are used most etc. Monitoring IP traffic flows facilitates more accurate capacity planning and ensures that resources are used appropriately in support of organizational goals. It helps IT determine where to apply Quality of Service (QoS), optimize resource usage, etc.
Note 1: To enable NetFlow and/or sFlow monitoring, the source device(s) must be first configured (using a vendor-specific method) to send NetFlow/sFlow packets to Net Inspector NetFlow collector service and the source devices must be set as a NetFlow source in Net Inspector. To set a device as a NetFlow source in Net Inspector, check the NetFlow source checkbox in the General tab of the respective device's New Device or Edit Device Monitoring Options dialog box.
Note 2: Net Inspector displays information received through both, NetFlow and sFlow protocol in the same way. In this documentation all references to NetFlow apply also to sFlow.
All NetFlow/sFlow reports are accessible from the NetFlow home page, as described in the NetFlow Home Page topic.