oss netflow collector/trending/analysis

There's also SiLK from CMU. It's powerful but has a learning curve.

I also see pmacct being used both by some end networks and by
some vendors as part of systems.


pmacct (http://www.pmacct.net/) is another pretty awesome open source tool.


SiLK is very good. See FlowViewer for a powerful front-end to the tool.


Also supports flow-tools.


Argus (qosient.com) is worth looking at.

Dave Edelman

Ntop is somehow open source if I recall. Seemed to work well and was fairly cheap to license.