How to use Netflow Plugin..?

How to use Netflow Plugin..?

We have installed netflow plugin on top of OPManager but when I tried to access the Netflow analyzer, it is saying that I should enable the Netflow/Sflow on the device or No such device with Netflow/Sflow export is found.
What can be the error?
Can I use netflow Plugin for Juniper Firewall or is it only for switch/router?How can I configure thge device to obtain the data using the Netflow plugin?
Also can we use Netflow Plugin for IPSEC VPN Monitoring?
 
Help is very much required at the earliest...
 
Thanks in Advance

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