IT technical memo of networking

CPU rate of increase by NetFlow enabled - Cisco

NetFlow is in a variety of routers and switches from Cisco, it can collect traffic information. At the time of use is expected to increase in CPU utilization, anxious performance impact. To introduce the performance impact and rate of rise of CPU usage when you enable NetFlow on Cisco routers.

CPU usage increase

But a little old, CPU usage rate of increase during the NetFlow use has been reported in Cisco official.

Excerpt information

Summary of Cisco report is as follow. The router models excerpt in a personal preference. Figures for those in the case of setting the two Exporter in NetFlow v9, describes the CPU usage at the time of each of the Flow/s. Flow number for different by the communication sequence of the system, it is necessary to estimate from bps, etc. of traffic.

NetFlow No / NetFlow Yes (CPU usage rate of increase)

Models 10,000Flow 45,000Flow 65,000Flow
Cisco 3845 7%/10%(+3%) 11%/20%(+9%) 13%/33%(+20%)
Cisco 7200 NPE-300 11%/18%(+7%) 27%/38%(+11%) 35%/51%(+16%)
Cisco 12000(v5) 7%/12%(+5%) 8%/23%(+15%) 11%/31%(+20%)
Average about 5% about 12% about 20%

Note that by the sampling , it is possible to reduce the performance impact suppress the increase CPU utilization. As the table below, you can significantly reduce the CPU usage.

Sampling rate CPU usage reduction rate
1: 100 75%
1: 1000 82%

How much of what is in the recent models required verification.


By enabling NetFlow, CPU utilization of the router will give rise to performance impact. Because such as described is a little old Cisco of the report, it is recommended to pre-verification in the model to be used at the time of introduction.

This Blog is English Version of my JP's.

Sorry if my English sentences are incorrect.