This blog post is for network experimenters who want to export flow records from a small network, such as a home network using an OpenWRT router. Such a network might look like this:
Flow records can be useful for various applications. Here is an example flow record:
Date first seen Duration Proto Src IP Addr:Port Dst IP Addr:Port Packets Bytes Flows 2018-08-04 21:31:34.518 0.000 TCP 10.1.1.19:52465 -> 10.1.1.1:22 100 4600 1
Flow records give a coarse-grained view of what traffic is passing over a network, including flow source and destination addresses/protocols/ports, as well as volume information such as packets and bytes.
In this tutorial we use OpenWRT, a popular free and open source router operating system, and add the softflowd package to it to generate NetFlow flow records. There are however many other options to achieve the same outcome. Continue reading