Network Traffic Monitor with vnStat

vnStat is a console-based network traffic monitor for Linux and BSD that keeps a log of network traffic for the selected interface(s). It uses the network interface statistics provided by the kernel as information source. This means that vnStat won’t actually be sniffing any traffic and also ensures light use of system resources. As it says on their website

opkg update
opkg install vnstati luci-app-vnstat

If you want language translation for the LuCI Webgui Integration then install the following: