tick
----
ip tunnel add tun6to4 mode sit remote any local `ifaceaddr ppp0`
ip link set dev tun6to4 up
ip -6 addr add "`ip6to4 ppp0`::1:2" dev tun6to4
ip -6 route add 2000::/3 via ::192.88.99.1 dev tun6to4 metric 1


ip -6 addr add "`ip6to4 ppp0`::2:1" dev eth0
ip -6 route add "`ip6to4 ppp0`::2:0/112" dev eth0
echo '1' >/proc/sys/net/ipv6/conf/all/forwarding 


tack
----
ip -6 addr add "`ssh tick ip6to4 ppp0`::2:2" dev eth0
ip -6 route add "`ssh tick ip6to4 ppp0`::2:0/112" dev eth0


ip -6 route add 2000::/3 via "`ssh tick ip6to4 ppp0`::2:1" dev eth0