#!/bin/sh
ifconfig gif create
gifconfig gif0 inet 71.174.X.X 213.121.X.X
&& ifconfig gif0 inet6 20XX:618:400::1:47ae:a3b5 prefixlen 128
&& route add -inet6 default fe80::%gif0
&& echo "IPv6 configuration completed" ||
{ echo "IPv6 configuration failed!" 1>&2; exit 1; }

To deactivate your tunnel simply copy and paste the following commands into a deactivation script just like above.

 #!/bin/sh
route delete -inet6 default fe80::%gif0
ifconfig gif0 inet6 20XX:618:400::1:47ae:a3b5 prefixlen 128 delete
gifconfig gif0 delete
&& echo "IPv6 un-configuration completed" ||
{ echo "IPv6 un-configuration failed!" 1>&2; exit 1; }