Has anyone come accross a situation where the couter on the graph shows for example eth0 has 117.02 inbound and 120.6 outbound but nothing is in the graph? I also have graphs displaying nothing and the couters have nan for data? This is weird because some graphs are working just fine.....
This is most likely because you're hitting the maximums for the monitors and RRDTool isn't recording the values. I'm pretty sure the defaults we have are for 100MBit interfaces (12000000). You probably want to increase this if you're doing > 12MB/s (ie, gigabit).
You probably want to modify the Template Linux Box ethernet monitors as well so when you create new graphs it will work.
I would recommend a value like 12000000000 or U.