digraph G {
    node [ shape=box ]
#    rankdir=LR;
    label="Making IPv4 reachable via IPv6 with the VIWIB"

    internet [ label="Internet (v6/v4)" shape=oval ]
    lan [ label="LAN\n2a0a:e5c1:XXX:cafe::/64\n192.168.1.0/24" shape=oval ]

    viwib [ label="VIWIB\n2a0a:e5c1:XXX::42\n192.168.1.42" ];
    v4only [ label="IPv4 only device\n (f.i. 192.168.1.1)" ]
    v6dev [ label="IPv6 device" ]
    ipv6vpn [ label="IPv6VPN.ch" shape=oval ]

    viwib->internet [ label="IPv4/IPv6 uplink via WAN interface" ]
    viwib->lan [ label="Provide IPv6, static IPv4 address" ]
    ipv6vpn->internet [ label="Route /48 IPv6 network to VIWIB" ]
    v4only->lan [ label="Knows only about 192.168.1.0/24" ]
    viwib->v4only [ label="Map 2a0a:e5c1:XXX:b00::/96\nto 192.168.1.0/24" style=dashed ]

    v6dev->v4only [ label="Access via 2a0a:e5c1:XXX:b00::192.168.1.1" style=dashed ]
}