I'm not sure if this will interfere with network manager:
The following is a list of variables that can be put in the configuration file, with an
example in parentheses. * marks the default. For the meaning of suffix, see the section
Choose when the interface should be set up.
manual Interface will be set up if ifup is called manually (without option boot or
auto Interface will be set up as soon as it is available (and service network was
started). This either happens at boot time when network is starting or via
hotplug when a interface is added to the system (by adding a device or load-
ing a driver). To be backward compliant onboot, on and boot are aliases for
This mode is nearly the same as auto. The difference between auto and hot-
plug is that the latter does not make rcnetwork fail if the interface cannot
be brought up.
The interface will be controlled from ifplugd. At initial ifup only ifplugd
will be started for this interface. Then if ifplugd detects a link if calls
ifup again which finally sets the interface up. See also variable
Nearly like auto, but interfaces with this startmode will never be shut down
via rcnetwork stop. ifdown <interface> still works. Use this when you use a
root filesystem via network.
off Will never be activated.
Using "STARTMODE=auto" might help.