High CPU on a 6504-E with Sup720 when Netflow Data Export is enabled.

Unanswered Question
Jun 21st, 2007

A customer of mine is having some issues with NetFlow Data Export. When they enable it on one of their 6500, all have sup720, the CPU gets very busy. The CPU peaks att 90 - 95%, and averages at 75-80%.

If they disable NetFlow Data Export the CPU peaks at 10-15% and averages at 5-7,5%.

The 6504 is running Native IOS, version 12.2.25SXF, and i cant find any caveates in the release notes that would explain this behavoiur.

Could anyone try to help me to find out why this is and try to fix this.

regards JockeW

I have this problem too.
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vkapoor5 Wed, 06/27/2007 - 05:56

The NetFlow-based features that this section describes apply to the Supervisor Engine 2 and Supervisor Engine 720 only.

NetFlow-based features always need to see the first packet of a flow in software. Once the first packet of the flow reaches software, subsequent packets for the same flow are hardware-switched.


Konstantin Dunaev Thu, 06/28/2007 - 07:17


just some idas:

1. on sup720 IOS 12.2 neflow is used only for statistic, it should not be used for traffic switching. be sure that your CEF engine is up and running.

2. Netflow feature on SUP720 is supported in HW, it should not influence the router CPU

3. try to use sampled NEtflow, may be router to much Netflow data to send out of interface and it leads to delays and high CPU load.

if you could post the config part with Netflow configuration on interfaces and global Netflow configuration.

jockew Mon, 07/16/2007 - 03:50

Sorry for the long time before my answer. I've been on vacation.

I will check the CEF settings and i will reply, with NDE config, as soon as i can get the configfile from the customer.

Regards JockeW

jockew Fri, 07/27/2007 - 03:12

Hi again.

The Netflow configuration is as follows:

mls netflow

mls flow ip interface-full

no mls flow ipv6

ip flow ingress

ip flow-export source Vlan801

ip flow-export version 5

ip flow-export destination 2055

mls aging long 64

mls aging normal 32

ip flow-cache timeout active 1

ip flow-cache timeout inactive 15

mls flow ip interface-full

mls nde sender version 7


Jocke W


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