The roadwarrior alice is sitting behind the NAT router moon but
at the outset of the scenario is also directly connected to the 192.168.0.0/24 network
via an additional eth1 interface. alice builds up a tunnel to gateway sun
in order to reach bob in the subnet behind. When the eth1 interface
goes away, alice switches to eth0 and signals the IP address change
via a MOBIKE ADDRESS_UPDATE notification to peer sun. Later the interface
comes back up again and because the best path is preferred (charon.prefer_best_path)
there is another switch to the directly connected path. alice sets
a virtual IP of 10.3.0.3, so that the IPsec policies don't have to be changed.