/etc/set_netflow.conf を作成して
# /usr/sbin/ngctl -f- <<-SEQ
mkpeer fxp0: netflow lower iface0
name fxp0:lower netflow
connect fxp0: netflow: upper out0
mkpeer netflow: ksocket export inet/dgram/udp
msg netflow:export connect inet/192.168.2.98:9997
# SEQ
netgraph を起動
/usr/sbin/ngctl -f /etc/set_netflow.conf