Well, if you get some sort of handle on it, please file a report. If you think it's a problem with NetworkManager proper and not Ubuntu- specific aspects of it, you can file a report upstream.
https://bugzilla.gnome.org/browse.cgi?product=NetworkManager ** Changed in: network-manager (Ubuntu) Status: Invalid => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/882929 Title: NM does not detect carrier on wired interface; ethtool does -- Atheros AR8152 atl1c To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/882929/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs