CloudFormation で Subnet に IPv6 CIDR を設定する

Resources:
  Vpc:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.128.0.0/16
  VpcCidrBlock:
    Type: AWS::EC2::VPCCidrBlock
    Properties:
      AmazonProvidedIpv6CidrBlock: true
      VpcId: !Ref Vpc
  Subnet:
    Type: AWS::EC2::Subnet
    Properties:
      CidrBlock: 10.128.0.0/24
      Ipv6CidrBlock: !Select
        - 0
        - !Cidr
          - !Select
            - 0
            - !GetAtt Vpc.Ipv6CidrBlocks
          - 1
          - 64
      VpcId: !Ref Vpc

ref

Fn::Cidr - AWS CloudFormation