Ipt-netflow is very fast and effective Netflow exporting module for Linux kernel. Designed for Linux router with heavy network load. This is netfilter/iptables module adding support for NETFLOW target. It's not using conntrack for performance reasons.
ipt-netflow version 1.4 has been released. This version have restored compatibility with popular kernel 2.6.18, added configure script, statistics improvements, some fixes for 64bit platforms, and minor performance tune up.
SourceForge.net Project Page:
http://sourceforge.net/projects/ipt-netflow/