基本的な2AZにまたがったネットワーク構成になります。
AWSTemplateFormatVersion: 2010-09-09
Parameters:
  VPCCidrBlock:
    Description: The primary IPv4 CIDR block for the VPC.
    Type: String
    MinLength: '9'
    MaxLength: '18'
    Default: 10.0.0.0/16
    AllowedPattern: '(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/(\d{1,2})'

  SubnetCidrBits:
    Description: Subnet CidrBits, alowed bitween 8 and 30.
    Type: String
    MinLength: '1'
    MaxLength: '2'
    Default: '24'
    AllowedPattern: '(\d{1,2})'

  PJPrefix:
    Type: String
    Default: base

Mappings:
  CidrBits:
    '30':
      bit: 2
    '29':
      bit: 3
    '28':
      bit: 4
    '27':
      bit: 5
    '26':
      bit: 6
    '25':
      bit: 7
    '24':
      bit: 8
    '23':
      bit: 9
    '22':
      bit: 10
    '21':
      bit: 11
    '20':
      bit: 12
    '19':
      bit: 13
    '18':
      bit: 14
    '17':
      bit: 15
    '16':
      bit: 16
    '15':
      bit: 17
    '14':
      bit: 18
    '13':
      bit: 19
    '12':
      bit: 20
    '11':
      bit: 21
    '10':
      bit: 22
    '9':
      bit: 23
    '8':
      bit: 24

Resources:
  VPC:
    Type: 'AWS::EC2::VPC'
    Properties:
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
      CidrBlock: !Ref VPCCidrBlock
      Tags:
        - Key: Name
          Value: !Sub '${PJPrefix}-VPC'
  PublicSubnet1:
    Type: 'AWS::EC2::Subnet'
    Properties:
      AvailabilityZone: !Select
        - 0
        - 'Fn::GetAZs': !Ref 'AWS::Region'
      CidrBlock:
        Fn::Select:
          - 0
          - Fn::Cidr:
            - Fn::GetAtt:
              - VPC
              - CidrBlock
            - 4
            - Fn::FindInMap:
              - CidrBits
              - !Ref SubnetCidrBits
              - bit
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !Sub '${PJPrefix}-PublicSubnet1'
      VpcId: !Ref VPC
  PublicSubnet2:
    Type: 'AWS::EC2::Subnet'
    Properties:
      CidrBlock:
        Fn::Select:
          - 1
          - Fn::Cidr:
            - Fn::GetAtt:
              - VPC
              - CidrBlock
            - 4
            - Fn::FindInMap:
              - CidrBits
              - !Ref SubnetCidrBits
              - bit
      AvailabilityZone: !Select
        - 1
        - 'Fn::GetAZs': !Ref 'AWS::Region'
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !Sub '${PJPrefix}-PublicSubnet2'
      VpcId: !Ref VPC
  PrivateSubnet1:
    Type: 'AWS::EC2::Subnet'
    Properties:
      CidrBlock:
        Fn::Select:
          - 2
          - Fn::Cidr:
            - Fn::GetAtt:
              - VPC
              - CidrBlock
            - 4
            - Fn::FindInMap:
              - CidrBits
              - !Ref SubnetCidrBits
              - bit
      AvailabilityZone: !Select
        - 0
        - 'Fn::GetAZs': !Ref 'AWS::Region'
      Tags:
        - Key: Name
          Value: !Sub '${PJPrefix}-PrivateSubnet1'
      VpcId: !Ref VPC
  PrivateSubnet2:
    Type: 'AWS::EC2::Subnet'
    Properties:
      CidrBlock:
        Fn::Select:
          - 3
          - Fn::Cidr:
            - Fn::GetAtt:
              - VPC
              - CidrBlock
            - 4
            - Fn::FindInMap:
              - CidrBits
              - !Ref SubnetCidrBits
              - bit
      AvailabilityZone: !Select
        - 1
        - 'Fn::GetAZs': !Ref 'AWS::Region'
      Tags:
        - Key: Name
          Value: !Sub '${PJPrefix}-PrivateSubnet2'
      VpcId: !Ref VPC
  InternetGateway:
    Type: 'AWS::EC2::InternetGateway'
    DependsOn: VPC
    Properties:
      Tags:
        - Key: Name
          Value: InternetGateway
  VPCGatewayAttachment:
    Type: 'AWS::EC2::VPCGatewayAttachment'
    DependsOn:
      - VPC
      - InternetGateway
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway
  PublicRouteTable:
    Type: 'AWS::EC2::RouteTable'
    Properties:
      Tags:
        - Key: Name
          Value: PublicRouteTable
      VpcId: !Ref VPC
  PublicRoute:
    Type: 'AWS::EC2::Route'
    DependsOn: VPCGatewayAttachment
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway
  PublicSubnetRouteTableAssociation1:
    Type: 'AWS::EC2::SubnetRouteTableAssociation'
    DependsOn:
      - PublicSubnet1
      - PublicRouteTable
    Properties:
      SubnetId: !Ref PublicSubnet1
      RouteTableId: !Ref PublicRouteTable
  PublicSubnetRouteTableAssociation2:
    Type: 'AWS::EC2::SubnetRouteTableAssociation'
    DependsOn:
      - PublicSubnet2
      - PublicRouteTable
    Properties:
      SubnetId: !Ref PublicSubnet2
      RouteTableId: !Ref PublicRouteTable
  ElasticIP1:
    Type: 'AWS::EC2::EIP'
    Properties:
      Domain: vpc
      Tags:
        - Key: Name
          Value: ElasticIP1
  ElasticIP2:
    Type: 'AWS::EC2::EIP'
    Properties:
      Domain: vpc
      Tags:
        - Key: Name
          Value: ElasticIP2
  NATGateway1:
    Type: 'AWS::EC2::NatGateway'
    Properties:
      AllocationId: !GetAtt
        - ElasticIP1
        - AllocationId
      SubnetId: !Ref PublicSubnet1
      Tags:
        - Key: Name
          Value: NATGateway1
  NATGateway2:
    Type: 'AWS::EC2::NatGateway'
    Properties:
      AllocationId: !GetAtt
        - ElasticIP2
        - AllocationId
      SubnetId: !Ref PublicSubnet2
      Tags:
        - Key: Name
          Value: NATGateway2
  PrivateRoutetable1:
    Type: 'AWS::EC2::RouteTable'
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: PrivateRouteTable1
  PrivateRoute1:
    Type: 'AWS::EC2::Route'
    DependsOn:
      - NATGateway1
    Properties:
      RouteTableId: !Ref PrivateRoutetable1
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NATGateway1
  PrivateSubnetRouteTableAssociation1:
    Type: 'AWS::EC2::SubnetRouteTableAssociation'
    Properties:
      RouteTableId: !Ref PrivateRoutetable1
      SubnetId: !Ref PrivateSubnet1
  PrivateRoutetable2:
    Type: 'AWS::EC2::RouteTable'
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: PrivateRouteTable2
  PrivateRoute2:
    Type: 'AWS::EC2::Route'
    Properties:
      RouteTableId: !Ref PrivateRoutetable2
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NATGateway2
  PrivateSubnetRouteTableAssociation2:
    Type: 'AWS::EC2::SubnetRouteTableAssociation'
    Properties:
      SubnetId: !Ref PrivateSubnet2
      RouteTableId: !Ref PrivateRoutetable2
  PrivateRoutetable3:
    Type: 'AWS::EC2::RouteTable'
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: PrivateRouteTable3