6to4 has always been broken, but that doesn't really matter because client preference for 6to4 has been <= 0.01% since 2013: https://www.google.com/intl/en/ipv

6to4 has always been broken, but that doesn't really matter because client preference for 6to4 has been <= 0.01% since 2013: https://www.google.com/intl/en/ipv6/statistics.html https://www.google.com/intl/en/ipv6/statistics.html