NFA5 & softflowd

I have 1 cisco router & 1 linux router.
NFA5 work with Cisco fine, but with linux router I have problems-
NFA dont show linux on Dashboard ( Device Group Management - linux in selected routers)
What's softflowd - http://www.mindrot.org/softflowd.html
(Softflowd is flow-based network traffic analyser capable of Cisco NetFlow� data export)
./softflowd -i eth0 -n 10.4.0.2:9996 -v 5

tcpdump:
11:46:01.176748 10.4.0.1.3628 > 10.4.0.2.9996: udp 1464 (DF)
11:46:01.177876 10.4.0.1.3628 > 10.4.0.2.9996: udp 1464 (DF)
11:46:01.179195 10.4.0.1.3628 > 10.4.0.2.9996: udp 696 (DF)
11:47:01.096168 10.4.0.1.3628 > 10.4.0.2.9996: udp 1464 (DF)
11:47:01.096996 10.4.0.1.3628 > 10.4.0.2.9996: udp 1464 (DF)
11:47:01.097763 10.4.0.1.3628 > 10.4.0.2.9996: udp 1416 (DF)

How I can solve this problem ?