NetworkManager drops config on link down

[Chris Adams]

I have a USB ethernet adapter on my desktop system that I use when
configuring new equipment (servers, routers, switches, etc.).  I have a
variety of pre-set configs in NM, like 192.168.0.x, 10.0.0.x, etc.

Often while configuring something, I need to reboot it, which drops the
link.  NM "helpfully" de-configures the interface, and I have to wait
for link to return and re-select the right config (because NM won't let
me select a config for an interface that is link-down).

Is there a way to disable this "helpfulness", so that for this USB
ethernet interface, once I select a config, it stays configured (even if
the link drops)?  This is frustrating behavior in many cases.