Get the most used interface

Hi!
I often use dummy0 interface, and "facter ipaddress" return often a wrong ip (the dummy0 one). I'm talking about linux.
My environment in usually a web server cluster where the node use arptables behind a load balancer.
I surely don't know a way to get the right order in /proc/net/dev to have the first not "^127" address be a usable address.
Sometimes facter ipaddress returns the right ip, sometimes returns the balancer ip. I think it depends on kernel version... don't know.
The most important problem of a not usable ip, for me, is a wrong ip in mysql storedconfig in puppet.

I think it is a problem that you just valutated.
This is my proposal.
If you don't like it, please suggest me a clean way to deliver this fact to my nodes. 
Actually, I brutally overwrite the file (horror)

Thanks for attention