According to Cisco, standard NetFlow exports use about 1.5 percent of the total analyzed switched traffic. Each datagram consists of up to 30 flows. NetFlow exportįlows are grouped for export into a NetFlow Export datagram. Data is expired and then exported from the cache to a NetFlow collector server at regular intervals based on flow timers.
A flow record is kept for each active flow. This data is condensed into a database within the network device called the NetFlow cache. Monitoring and grouping every packet forwarded by a router or switch generates a lot of data. Any variation in the value of any one of the parameters creates a new flow. Each additional packet with the same parameters (source and destination IP addresses, source and destination port, class of service) is grouped into a single flow. A flow is generated by the first packet passing through the standard switching path. These sets can be configured based on matching attributes in each packet, including:Īs each packet is forwarded, the respective attributes are examined. A flow is a way of grouping a unidirectional stream of packets into a specific set.
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