A minimal layer intended to be "mixed in" with the Docker Layer to provide Flannel based Overlay Networking to Docker Container infrastructure
This will probably go away into a more generic libnetwork abstraction when docker 1.9 launches.
iface The interface to configure the flannel SDN binding. If this value is empty string or undefined the code will attempt to find the default network adapter similar to the following command:
route | grep default | head -n 1 | awk {'print $8'}