I have a Billion 7401 VGP router connected to a commercial ISP (ADSL). I have configured a Linux machine to connect via MRTG regularly to collect statistics on the line. I noticed the following recently, which looked different to normal:
"4" indicates wireless, "5" indicates "bridge" and "6" indicates "ppp-channel". I'm not sure if I have configured it correctly -- I usually just look at graph "6" for the overall usage.
What I cannot explain is the usage in green on the very left of the "6" graph -- it is not reflected elsewhere in any of the other graphs. The graphs for "6" over different time-periods (not shown here) allowed me to calculate that the block of "green" data ran for about 6 hours at the same speed -- pulling down around 1GB of data. It started suddenly at the indicated speed, ran for about 6 hours, and ended almost as suddenly.
What is the "ppp-channel" and what could explain that usage if it is not reflected on the ethernet or the wireless ports? From what I can determine, only the Linux box was connected during that time and it was not downloading 1GB that I am aware of.