[afnog] CPU and memory usage -- Netflow

Mark Tinka mtinka at africaonline.co.zw
Thu Mar 29 11:43:25 UTC 2007

On Thursday 29 March 2007 13:03, Mike Barnard wrote:

> For those running netflow on their routers, i would like to know
> the payload on CPU and memory on a router when netflow is
> enabled,...

We are running Netflow on an NPE-G1 with full memory, seeing an 
average 2% CPU utilization (peaking at 3%). After 2 full BGP feeds 
and what-not, free operating memory sits at about 705MB.

This includes Netflow running on 3 interface, but then again this 
router is only handling about 10-13Mbps worth of traffic.

> especially for routers in an IXP.

We ran Netflow once on a heavily-configured 3640 doing about 12Mbps. 
CPU utilization didn't look great, but we swapped this router out 
for a 7200-VXR. The 3640 is now doing some exchange point work, but 
haven't enabled Netflow on it yet; that said, expect little or no 
comparably technical difference when deploying Netflow, say, 
against your upstream interfaces.

> And in general, where best on the network would one collect
> netflow data?

We monitor interfaces at the edge of the network, i.e., where PoP's 
enter into the core, where customers enter into the edge network, 
where upstream providers enter into the border routers.

These would be typical, but you may have requirements that would 
necessitate you running Netflow in another part of the network, or 
even for your customers.

> and what version of netflow would one consider for 
> any given situation?

We export version 5 data, which gives us mostly what we need at the 
moment (including ASN's).

Hope this helps.

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