The roadwarriors carol and dave set up a connection each to gateway moon and request a virtual IP via the IKEv2 configuration payload by using the leftsourceip=%config parameter. The dhcp plugin on gateway moon then requests an IP address and DNS/WINS server information from DHCP server venus using the DHCP protocol. The IP addresses are assigned statically by venus based on the user-defined MAC address derived by the dhcp plugin from a hash over the client identity. This deterministic MAC generation is activated with the strongswan.conf setting charon.plugins.dhcp.identity_lease = yes.

With the static assignment of 10.1.0.30 and 10.1.0.40, respectively, carol and dave become full members of the subnet 10.1.0.0/16 hidden behind gateway moon. And this thanks to the farp plugin through which moon acts as a proxy for ARP requests e.g. from alice who wants to ping carol and dave.