The roadwarriors carol and dave set up a connection each to gateway moon. Both carol and dave request the same virtual IP via the IKEv2 configuration payload by using the leftsourceip=PH_IP_CAROL1 parameter. On a first-come, first-served basis, carol gets PH_IP_CAROL1 from the simple address pool managed by gateway moon and dave gets the next free address PH_IP_DAVE1 from the pool.
leftfirewall=yes 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.