I am testing J-Flow (Netflow) on an SRX-240 with ntop 4.0.3.  I have J-Flow 
sampling set to (1) - which I believe means "sample" every packet.

Concerning "throughput" and possibly other metrics (such as total traffic / 
Bytes transferred):

 - SRX CLI show apx. 25Mb/s; 3,000 pps.
 - Cisco Switch interface statistics agree with this - within acceptable 
tolerances
 - ntop "Netflow" statistics agree with this - within acceptable tolerances

HOWEVER

nTop reports such as: "Summary Network Load", "Summary Traffic", "All Protocols 
Traffic"  do NOT agree with "reality", typically showing a max of 4Mb/s 500pps.

I have the flow-cache export timers set to 60 for active and 15 for inactive.  
I've been over 15Mb/s average with peaks of 30Mb/s for some time now, so this 
isn't just a quick burst that would get averaged out over time and appear less 
than reality.

At this point I can't say where the problem lies.  I would think if the ntop 
netflow stats align with the SRX interface stats that means the SRX is 
exporting the flow records accurately - but just a guess....

Any ideas or thoughts on next steps?

Gary









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