Provides stateless destination IPv6-to-IPv6 Network Prefix Translation (as described by RFC 6296).

You have to use this target in the mangle table, not in the nat table. It takes the following options:

--src-pfx [prefix/length]
    Set source prefix that you want to translate and length

--dst-pfx [prefix/length]
    Set destination prefix that you want to use in the translation and length

You have to use the SNPT target to undo the translation. Example:

    ip6tables -t mangle -I POSTROUTING -s fd00::/64 -o vboxnet0 -j SNPT --src-pfx fd00::/64 --dst-pfx 2001:e20:2000:40f::/64

    ip6tables -t mangle -I PREROUTING -i wlan0 -d 2001:e20:2000:40f::/64 -j DNPT --src-pfx 2001:e20:2000:40f::/64 --dst-pfx fd00::/64

You may need to enable IPv6 neighbor proxy:

    sysctl -w net.ipv6.conf.all.proxy_ndp=1

You also have to use the NOTRACK target to disable connection tracking for translated flows.