What is the difference between NetFlow version 5 and 9?

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NetFlow version 5 and version 9 have the following differences¹²³:

  • NetFlow version 5 generally supports ingress flow export only; NetFlow version 9 supports both ingress and egress export.
  • NetFlow version 5 is fixed in terms of the fields you can match and export; NetFlow version 9 is template-based, meaning you can freely choose which fields you’d like to have present in the exported NetFlow packets.
  • NetFlow version 9 includes additional information such as BGP origin AS, MAC addresses, VLAN IDs, and other router performance characteristics; NetFlow version 5 does not.
  • NetFlow version 9 is the IETF standard mechanism for information export; NetFlow version 5 is not.

If you want more details, please refer to the official Cisco documentation³.

Sources:
(1) What are two differences between NetFlow version 5 and NetFlow version …. https://vceguide.com/what-are-two-differences-between-netflow-version-5-and-netflow-version-9-select-2-2/.
(2) NetFlow v9 vs. NetFlow v5: What are the differences?. https://learningnetwork.cisco.com/s/question/0D53i00000Kt31ICAR/netflow-v9-vs-netflow-v5-what-are-the-differences.
(3) NetFlow version 9 – Cisco. https://www.cisco.com/c/en/us/products/ios-nx-os-software/netflow-version-9/index.html.
(4) NetFlow v5 and NetFlow v9 for interface index support – SolarWinds. https://support.solarwinds.com/SuccessCenter/s/article/NetFlow-v5-and-NetFlow-v9-for-interface-index-support?language=en_US.
(5) Netflow Version 5 or 9? + Configuration on a Cisco 6500. https://community.cisco.com/t5/routing/netflow-version-5-or-9-configuration-on-a-cisco-6500/td-p/2410544.