Gnome Network Manager - A must read note

When trying to figure what's happening for my NetworkManager settings being in-consistent with the settings in original interface control file /etc/network/interfaces, I found this note:

Why won't Network Manager manage my Networks?

If your network connection is listed in /etc/network/interfaces, it is unavailable to NetworkManager with it's default setup (read this to see how to change it to manage these connections: http://wiki.debian.org/NetworkManager ). The best option for a standard setup is to open the file using

sudo gedit /etc/network/interfaces 

and comment out (ie put a # in front of) or delete every line in the /etc/network/interfaces file except the two with lo in them- they read

auto lo
iface lo inet loopback

Things are you really want to manage static IP yourself. Then you add new line in /etc/network/interfaces, remember, but not in Network Manager. Any non-dhcp (static) interface in /etc/network/interfaces will not be governed by NetworkManager. Then you may ignore the alert icon on NetworkManager even if you have connection access to the outside with your static interface settings.