graph G {
    node [ shape="box"];
    rankdir="LR";

    x520_1 [ label="X520: IPv4" ];
    x520_2 [ label="X520: IPv6" ];
    x520_nsg_1 [ label="X520: IPv4" ];
    x520_nsg_2 [ label="X520: IPv6" ];

    subgraph cluster_esprimo {
        label="Load generator";

        x520_1;
        x520_2;
    }

    subgraph cluster_nsg {
        label="NAT64 Host";

        x520_nsg_1;
        x520_nsg_2;
    }

    x520_1--x520_nsg_1;
    x520_2--x520_nsg_2;

}