how to turn off automatic switch from wifi to cable?

[Radoslaw Garbacz <rgarbacz googlemail com>]

Hi,

I would like to use my machine as a router. My wifi is connected to
the Internet, and my ethernet I would like to use for a local network.
For now any time I plug-in the cable NetworkManager disconnects wifi.
Is there a way to make it more flexible, to configure it, or to
disable the automatic switch?

Thanks in advance.

-- 
Radoslaw Garbacz