This is actually quite widely used (see [1]). The big limitation is that all connections have to be initiated from the IPv6 side, so it's usually used to allow

This is actually quite widely used (see [1]). The big limitation is that all connections have to be initiated from the IPv6 side, so it's usually used to allow v6-only client networks to access v4 servers, but even that is a big win for bootstrapping - for example, it's let T-Mobile configure all its new Android devices for IPv6-only behind a variant of NAT64. Another cool trick is IPv4-mapped IPv6 addresses [2], which lets userspace software act like the IPv4 internet is just a subnet of the IPv6 internet, and speak IPv6 only, while the network stack of the host system deals with the annoyances of dual-stack. (In fact, I think on Linux systems this will even let you pretend that an IPv4-only configuration is actually IPv6 ;-) ). [1] http://en.wikipedia.org/wiki/NAT64 http://en.wikipedia.org/wiki/NAT64 [2] https://tools.ietf.org/html/rfc4038#section-4.2 https://tools.ietf.org/html/rfc4038#section-4.2