improved version of 6to4: 6rd has the good things of 6to4 (easy IPv6
over IPv4 tunnel technique), but has taken care of one of the Bad
Things of 6to4: with 6rd the IPv6-over-IPv4 tunnel is completely
handled by the customer's own ISP, instead of some random unknown 6to4
gateway on the Internet. So, with 6rd you get an IPv6 from your ISP,
not a 2002: address.
IMHO, one Bad Thing of 6to4 remains in 6rd: it is not desgined to work
from behind NAT. In my experience, 6to4 might or might not work behind
NAT: It depends on the NAT device: does it handle Protocol 41 or GRE
tunnels. Brrr ...
So the best solution is the deploy 6rd / 6to4 on the NAT device
itself. So far, only Free has deployed 6rd on it's self-developed
Freebox. So the wait continues for the usual suspects: when do Thomson
Speedtouch, Zyxel, Linksys, AVM Fritzbox deploy 6rd on their DSL