This is usually delivered as a professional service engagement by Extreme. It takes some time to do it effectively.
But in essense,
One takes a trace at the point of the Netflow collector interface (assuming it's online, if not, any IP to a PC will do, send Netflow to that IP address of the sniffer)
Start filtering Netflow on port udp 2055. Each netflow packet generally has 20+ flows in it (expand it to look at it). Capture a minutes worth of traffic. Do this several times through the day, at peak traffic periods. This will give a general idea of the effective average flow rate in a one minute span, assuming the flows are being delivered within a one minute interval, which is generally the case.
If your using a Extreme PV-FC-180 or S-Series device, you can also look at the commands samples at a one minute interval
loop 5 60show flow statThis command shows all flows unique to a port. With uplinks, there is likely overlap you would want to avoid when enabling Netflow. Generally you want to set to rx only on a port.
Also,
loop 5 60 show netflow stat
This shows the amount of packets that are able to be exported over a minutes timeframe.
The loop command ask for 5 samples at 60 second intervals, and will print the data to the screen. Use 'set length 0' first if your paging is enabled. Capture all data to a log buffer for later review.
