NetFlow v5: Is the most popular and most basic of all four formats that are being discussed in this blog. It is ideal if you are simply interested in seeing the classic source and destination IP addresses, source and destination ports and the bytes count of transferred data. What makes NetFlow v5 special compared to its predecessors is the added BGP autonomous system information and flow sequence numbers. One limitation of NetFlow v5 is that you can only enable ingress flow export on an interface. Most Cisco devices that are running IOS 11.1 and above support v5.
NetFlow v9: Is an upgrade to NetFlow v5. On top of the traditional flow record of v5, it was an enhancement to support different technologies such as Multi-cast, IPSec, and Multi Protocol Label Switching (MPLS). These enhancements are mostly due to the addition of support for egress flow export. It is supported in IOS 12.4 and above.
Flexible NetFlow: The major difference between NetFlow v9 and Flexible NetFlow is the ability to selectively export data. You basically get to choose what flow information you want to export. That is why it is said to be “flexible.” Due to its support for DPI, on top of what’s already part of v9, it brings NBAR, Voice over IP and video traffic monitoring, unlimited flow collectors, IPv6 and more. Most of the latest Cisco IOS releases support FnF.
IPFIX: Is the Cisco proposed standard for IP flow information export and was designed based on NetFlow v9. Several vendors have already adopted IPFIX (e.g. Juniper, Avaya, SonicWALL, nBox, etc.).
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