digraph G {
    node [ shape=box ]

    label="Standard IPv4 NAT"

    v4lan [ label="IPv4 LAN\n192.168.x.y/24" ]
    router [ label="Router/Firewall\nPublic IP address" ]
    v4internet [ label="IPv4 Internet\n0.0.0.0/0" ]

    v4lan->v4internet [ label="Connects via NAT" style=dashed ]
    v4lan->router [ label="Connects via default route" ]
    router->v4internet [ label="Masquerades 192.168.x.y\nto public IP address" ]

}