The roadwarriors carol and dave set up a connection each to gateway moon.
Both carol and dave request a virtual IP via the IKEv2 configuration payload.
The gateway moon assigns virtual IP addresses from a simple pool defined in the pools section
of swanctl.conf in a monotonously increasing order.
The updown script automatically inserts iptables-based firewall rules that let pass
the tunneled traffic. In order to test the tunnels, carol and dave then ping
the client alice behind the gateway moon. The source IP addresses of the two
pings will be the virtual IPs carol1 and dave1, respectively.