ifconfig sit0 up
ifconfig sit0 inet6 tunnel ::216.66.87.14
ifconfig sit1 up
ifconfig sit1 inet6 add 2001:470:1f1a:21e::2/64
route -A inet6 add ::/0 dev sit1
QuoteIf you have "ip" available, using it to bring up the tunnel is cleaner.
ifconfig sit1 inet6 add 2001:470:1f1a:21e::2/64 tunnel ::216.66.87.14 up
route -6 add default dev sit1