[Internet]
      |
+-----+-----------+
| FW that filters |
| 6to4 / proto-41 |
+-----+-----------+
      |
      |             +--------------------------------+
      |     1.2.3.4 |    Router that does NAT44 and  |
    [ISP]---------(WAN)  6to4 tunneling+routing      |
    2002:102:304::1 |    (Apple Airport Extreme?)    |
                    |    (Windows w/ICS enabled?)    |
                    |    (Other SOHO router model?)  |
                    +-------------------(LAN)--------+
                        2002:102:304:1::1 | 192.168.1.1
                        (SLAAC or DHCPv6) | (DHCPv4)
                                          |
        2002:102:304:1:21c:bfff:fe02:f2a5 | 192.168.1.2
      +-----------------------------------+-------------+
      |                                                 |
      |   OS X or Linux host - prefers 6to4 over IPv4   |
      |                                                 |
      +-------------------------------------------------+