Are there any (not a resource hog) solutions to have statistics about the traffic on an OpenWrt router? :O e.g.: traffic per IP address, monthly statistics, etc. :O
To monitor traffic and other information about my OpenWrt router I use munin. I detail my experience in my posting on Monitoring with Munin. It doesn't specifically address traffic by IP address, which a tool like
ntop might be better suited for.
The firewall can be configured to gather such accounting data, but you would need to extract and summarize it. I use shorewall-lite to build my firewall rules. I haven't posted on my experiences yet.
Traffic reporting on OpenWRT is not much different than on other Linux platforms. You can use a shell to look at the interface statistics or use one of the several reporting / monitoring packages.
Personally I use collected to gather some data from my OpenWRT routers and build graphs on another machine along with some other relevant data.
Just trying collectd
I'm following this neat article, and it is great