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NetFlow was originally a Cisco packet switching technology for Cisco routers, implemented in [[Cisco IOS|IOS]] 11.x around 1996.
It was originally a software implementation for the Cisco 7000, 7200 and 7500,<ref name="netflow switching">http://www.cisco.com/en/US/docs/ios/11_2/feature/guide/netflow.html</ref> where it was thought as an improvement over the then current Cisco Fast Switching. Netflow was invented by Darren Kerr and Barry Bruin <ref>https://www.cisco.com/c/dam/en/us/products/collateral/security/ios-network-foundation-protection-nfp/prod_presentation0900aecd80311f49.pdf</ref>from Cisco (U.S. patent # 6,243,667).
The idea was that the first packet of a flow would create a NetFlow switching record. This record would then be used for all later packets of the same flow, until the expiration of the flow. Only the first packet of a flow would require an investigation of the route table to find the most specific matching route. This is an expensive operation in software implementations, especially the old ones without [[Forwarding information base]]. The NetFlow switching record was actually some kind of route cache record, and old versions of IOS still refer to the NetFlow cache as '''ip route-cache'''.
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