Why only 'lo' interface ?
After logging in SDN-VM, I realized that only a localhost interface was up, though I had properly set relative parameters in the virtual machine's preferences pane.
Investigations
The command, 'ifconfig eth0 up', also didn't work, which means the network protocol stack didn't have any information about 'eth0' interface. So, I checked the network interface information files such as /etc/network/interfaces, and it turned out kernel had failed to load the device. (Because the relative PCI controller, and ethernet device drivers were already loaded.)
The only thing left was checking whether UDEV worked properly or not.
As expected, the udev rules file for network had different MAC addresses, I don't know where they came from though.
A Workaround
Easy.
The investigation showed both the problem and the solution.
After fixing the file, I rebooted SDN-VM, and saw the interfaces correctly loaded.
