Enter a 64-bit address prefix to use on the tunnel interface. You will be prompted for additional address prefixes until you press [Enter] in response to this prompt.      

If a router is not advertising a global address prefix on the tunnel interface, enter a 64-bit address prefix. When you are finished entering prefixes, press [Enter].      

If you do not want the host to use an IPv6 address prefix on the tunnel interface, press [Enter].