How to setup Netflow for FreeBSD and Linux.

On FreeBSD:

/usr/sbin/ngctl -f- <<-SEQ
        mkpeer re0: netflow lower iface0
        name re0:lower netflow
        connect re0: netflow: upper out0
        mkpeer netflow: ksocket export inet/dgram/udp
        msg netflow:export connect inet/10.10.0.250:2222
SEQ

... wbere re0 is for example the interface inside or outside

By default it's v5 flows.  Interval is fixed.

On Linux:

[Hervey]

To see not just the inside->outside traffic, but also
the traffic generated by the noc machine itself, the trick is
to use INTERFACE="any" in /etc/default/softflowd.

[Brian]

To see IPv6 flows use -v 9. To break up long-lived flows use -t maxlife=5m

~~~
INTERFACE="br-lan"
OPTIONS="-n 10.10.0.250:9991 -v 9 -t maxlife=5m"
~~~