Stefan
By not-routable... I did mean not route-able over the Internet... of course you could do it for a private local lan environment.
It might be a sw problem but it could be a topology/implementation issue... Were the machines VMs, were they LXC
containers, was x2goserver in a IaaS cloud somewhere, was it just a PC/laptop on a private network. Were these different machines in different networks and do they get rebooted and assigned new IP addresses?
sorry for the confusion... just wanted to ask the questions.