UPDATES! 21/6/14: Use a different interface that does just WAN traffic and made the cron thing actually work. Scroll down for the green bits (padavans firmware only though).
I’ve spent the last few days fiddling around with network traffic monitoring on my modem so I can track downloads for each different computer on my network. This article is a how to guide and a set of notes about getting it working.
If you want to follow this guide, you will need an Asus RT-N56U or one of the similar models. You can also mostly follow this guide using any OpenWRT routers (but you will need to adjust as you go to suit your router). I initially set it up using the stock firmware on the RT-N56U, however I ran into issues where it was reporting the wrong amount of traffic. After I installed the Padavan’s Firmware, I still had the same problem (I later solved it by disabling hardware NAT below). In theory this technique should work with the stock firmware and I’ll detail it below as well as how to get Padavan’s Firmware up and running too.
The final result of this is to be able to see a screen like this:
