ipv6Prefix Count
Parameters
value
The number of IPv6 prefixes to assign to a network interface. When you specify a number of IPv6 prefixes, Amazon EC2 selects these prefixes from your existing subnet CIDR reservations, if available, or from free spaces in the subnet. By default, these will be /80 prefixes. You can't specify a count of IPv6 prefixes if you've specified one of the following: specific IPv6 prefixes, specific IPv6 addresses, or a count of IPv6 addresses.