Hello,

I have a Cisco ASA configured to send Netflow to an instance of nprobe, and 
then on to ntopng.
The configuration is working, however I have noticed that nprobe is only 
emitting flows when it receives a flow-teardown event from the ASA. This is 
causing inaccurate bandwidth reporting for long-lived flows as the total byte 
count is being recorded as a single spike once the flow is torn down.

My understanding is that Cisco ASA netflow is very non-standard and that this 
behaviour used to be expected on older version of ASA. However, newer versions 
of ASA are capable of sending flow-update events using a refresh-interval for 
active flows. When I run tcpdump on my nprobe server I can see the flow-create 
and flow-update events being sent from the ASA, however nprobe does not seem to 
use these events, or act on them in any way. I have enabled verbose logging, 
but can only see logs being generated for flow-teardown events, not flow-create 
or flow-update.

My question is, should I expect nprobe to use the flow-updates from Cisco ASA 
for long-lived active flows, or is it normal for it to only process 
flow-teardown events?

Nprobe (dev build v.8.1.170626)  is running in collector mode with the 
following settings:

--zmq="tcp://*:5559"
--collector-port=2055
-i=none
-n=none



Regards,
Pelham

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