Explanation/Reference:
Section: Design Methodologies Explanation
Explanation:
NetFlow is a Cisco IOS feature that can collect timestamps of traffic flowing between a particular source and destination. NetFlow can be used to gather flow-based statistics, such as packet counts, byte counts, and protocol distribution. A device configured with NetFlow examines packets for select Layer 3 and Layer
4 attributes that uniquely identify each traffic flow. The data gathered by NetFlow is typically exported to management software. You can then analyze the data to facilitate network planning, customer billing, and traffic engineering. A traffic flow is defined as a series of packets with the same source IP address, destination IP address, protocol, and Layer 4 information. Although NetFlow does not use Layer 2 information, such as a source Media Access Control (MAC) address, to identify a traffic flow, the input interface on a switch will be considered when identifying a traffic flow. Each NetFlowenabled device gathers statistics independently of any other device? NetFlow does not have to run on every router in a network in order to produce valuable data for an audit. In addition, NetFlow is transparent to the existing network infrastructure and does not require any network configuration changes in order to function.
Reference:
Cisco: Cisco IOS Switching Services Configuration Guide, Release 12.2: NetFlow Overview