Same ip addresses for several virtual hosts when two marionnet are running

May be the first question is: do we need to be able to run multiple instances of marionnet
on the same machine? If the answer is no, the daemon (anyway unique) must block in some way creation of new
instances. If the answer is yes, the above requirement is mandatory.
Actually, addresses used are 172.23.x.y for the virtual machines
and 172.23.0.254 for the host. We can use other class B private addresses from 172.16 to 172.31.
Of course it may be a problem if the user choose the same kind of address for one of its network,
since it must be fixed before user's choice -- this is the price of the magic !
Ghostifiy interface for marionnet management/display is a nice idea to help beginners to start using marionnet,
but I think there is at least a need of an explicit warning at the virtual machine level (may be in /etc/motd).

In fact, at IUT-Orsay, we used this year Marionnet for exams with an automatic scoring system (I can publish the scripts in a "contrib" section of Marionnet when it will be really usable).
Several students pass their examination on the same machine, one after another.
To overcome a possible problem with the scoring system, we used several X servers so when a student finished, we switched the screen on another X server and let all the Marionnet instances running (in order to eventually connect with ssh on the machines to check).
So running several instances of Marionnet can be sometimes useful, but in this case we manually (i.e. with a script) add another ip address on eth42 on the virtual machine to overcome this difficulty.

May be the easiest change would be adding a parameter for the management network in the config file (/etc/marionnet/marionnet.conf or ~/.marionnet, ...) :

MARIONNET_ADMIN_NETWORK = 172.23.0.0/24