Having edited the ifplugd.script (just changed an ethtool call to advertise 10 Full instead of 100/100 Full) we lost contact with the device. As it turns out we can get contact on it on IPv6 now, and only that. How could this happen, and how do we reverse it? We are unable to discover the device via MAX so no simple reconfig/reimaging there...But we can SSH onto it using IPv6.