digraph G {
    node [ shape=box ]
    #rankdir=LR;

    label="k8s: IPv6 vs. IPv4 DNS service"

    subgraph cluster_ipv4 {
             label="IPv4"
             serverv4 [ label="DNS server" ]
             kubev4 [ label="kube-dns Service (IPv4, RFC1918)" ]
             magicbox [ label="Magic Box\nTunnel, VPN, etc." ] ;
    }
    subgraph cluster_ipv6 {
             label="IPv6"

             serverv6 [ label="DNS server" ]
             kubev6 [ label="kube-dns Service (IPv6)" ]
    }

    serverv4->magicbox
    magicbox->kubev4
    serverv6->kubev6

}