Very fast and effective Netflow exporting module for Linux kernel. Designed for Linux router with heavy network load. It is iptables module, but not using conntrack for performance reasons.
ipt-netflow version 1.2 has been released. This version have stability enhancements, documentation improvements, ip frag support, better statistics.
SourceForge.net Project Page:
http://sourceforge.net/projects/ipt-netflow/