I've got a problem with Gnome Boxes:I've 2 machines, cloned 1 from other, with CentOS. Both machines get same IP addr on Gnome Boxes, so when I boot 2nd, 1st gets disconnected from network, and vice-versa. This is not acceptable behaviour,and I've been struggling to find out why does this happen for quite some time. 
Gnome Boxes: proper network configuration?
networking;gnome;virtual machine
What I've found out is that Gnome Boxes & Libvirt save mac-address for machines in config located here:/home/$USER/.config/libvirt/qemu  So, to fix the issue, both machines must have different Mac-addresses, which can be fixed only by editing those files. Didn't find any relevant option in Gnome Boxes GUI. 