Cloudformation template for a simple AWS VPC with three public, three private subnets, IGW, route tables and CF exports for all subnet Ids

my-vpc.yaml

---
AWSTemplateFormatVersion: '2010-09-09'
Description: Creates AWS infrastructure for the primary (non default) VPC
Parameters:
  VPCOctet:
    Description: First two octets of the VPC (e.g. '192.168' for '192.168.0.0/20')
    Type: String
    MinLength: 4
    MaxLength: 7
    AllowedPattern: "[0-9]{2,3}.[0-9]{1,3}"
    ConstraintDescription: Must only be the first two octets without a trailing period
    Default: '172.16'
  VPCName:
    Description: The name for the VPC
    Type: String
    MinLength: 3
    MaxLength: 255
    Default: 'my-aws-vpc'

Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties: 
      CidrBlock: !Join [".", [!Ref VPCOctet, '0.0/20'] ]
      InstanceTenancy: default
      Tags:
        - Key: Name
          Value: !Ref VPCName
        - Key: VpcOctet
          Value: !Ref VPCOctet

  PublicSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Join ["",  [!Ref 'AWS::Region', a]]
      CidrBlock: !Join [".", [!Ref VPCOctet, '1.0/24'] ]
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, pub , a] ]
      VpcId: !Ref VPC

  PublicSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Join ["",  [!Ref 'AWS::Region', b]]
      CidrBlock: !Join [".", [!Ref VPCOctet, '2.0/24'] ]
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, pub ,b] ]
      VpcId: !Ref VPC

  PublicSubnetC:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Join ["",  [!Ref 'AWS::Region', c]]
      CidrBlock: !Join [".", [!Ref VPCOctet, '3.0/24'] ]
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, pub , c] ]
      VpcId: !Ref VPC

  PrivateSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Join ["",  [!Ref 'AWS::Region', a]]
      CidrBlock: !Join [".", [!Ref VPCOctet, '5.0/24'] ]
      MapPublicIpOnLaunch: false
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, private, a] ]
      VpcId: !Ref VPC

  PrivateSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Join ["",  [!Ref 'AWS::Region', b]]
      CidrBlock: !Join [".", [!Ref VPCOctet, '6.0/24'] ]
      MapPublicIpOnLaunch: false
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, private, b] ]
      VpcId: !Ref VPC

  PrivateSubnetC:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Join ["",  [!Ref 'AWS::Region', c]]
      CidrBlock: !Join [".", [!Ref VPCOctet, '7.0/24'] ]
      MapPublicIpOnLaunch: false
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, private, c] ]
      VpcId: !Ref VPC

  IGW:
    Type: AWS::EC2::InternetGateway
    Properties:
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, igw] ]

  AttachIGWtoVPC:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref IGW

# uncomment this section to add a NAT Gateway to a public subnet to permit resources deployed into
# private subnets to reach the internet
# do not uncomment this section unless you actually need it as it will incur additional costs
#  NatGatewayAttachment:
#    Type: AWS::EC2::EIP
#    DependsOn: AttachIGWtoVPC
#    Properties:
#        Domain: vpc

#  NatGateway:
#    Type: AWS::EC2::NatGateway
#    Properties:
#      AllocationId: !GetAtt NatGatewayAttachment.AllocationId
#      SubnetId: !Ref PublicSubnetA
#      Tags:
#        - Key: Name
#          Value: !Join ["-", [!Ref VPCName, nat] ]
 
  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, public, rt] ]

  PublicRouteTableIGWRoute:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref IGW

  RouteTableAssPubA:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PublicRouteTable
      SubnetId: !Ref PublicSubnetA

  RouteTableAssPubB:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PublicRouteTable
      SubnetId: !Ref PublicSubnetB

  RouteTableAssPubC:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PublicRouteTable
      SubnetId: !Ref PublicSubnetC

  PrivateRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: !Join ["-", [!Ref VPCName, private, rt] ]

  RouteTableAssPrivateA:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTable
      SubnetId: !Ref PrivateSubnetA

  RouteTableAssPrivateB:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTable
      SubnetId: !Ref PrivateSubnetB

  RouteTableAssPrivateC:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTable
      SubnetId: !Ref PrivateSubnetC

  SecretsManagerInterfaceEndpoint:
    Type: AWS::EC2::VPCEndpoint
    Properties:
      PrivateDnsEnabled: true
      VpcEndpointType: 'Interface'
      ServiceName: !Sub com.amazonaws.${AWS::Region}.secretsmanager
      VpcId: !Ref VPC
      SubnetIds: 
        - !Ref PrivateSubnetA
        - !Ref PrivateSubnetB
        - !Ref PrivateSubnetC
      SecurityGroupIds:
        - sg-0cxxxxxxxxxxxxxxx #change this

  SnsInterfaceEndpoint:
    Type: AWS::EC2::VPCEndpoint
    Properties:
      PrivateDnsEnabled: true
      VpcEndpointType: 'Interface'
      ServiceName: !Sub com.amazonaws.${AWS::Region}.sns
      VpcId: !Ref VPC
      SubnetIds: 
        - !Ref PrivateSubnetA
        - !Ref PrivateSubnetB
        - !Ref PrivateSubnetC
      SecurityGroupIds:
        - sg-0cxxxxxxxxxxxxxxx #change this

Outputs:
  VPCID:
    Value: !Ref VPC
    Description: ID of the VPC deployed
    Export:
      Name: !Join ["-", [vpc, id]]

  VPCCidrBlock:
    Value: !GetAtt VPC.CidrBlock
    Description: ID of the VPC deployed
    Export:
      Name: !Join ["-", [vpc, cidr]]

  PublicSubnetA:
    Value: !Ref PublicSubnetA
    Description: ID of the public subnet
    Export:
      Name: subnet-pub-a

  PublicSubnetB:
    Value: !Ref PublicSubnetB
    Description: ID of the public subnet
    Export:
      Name: subnet-pub-b

  PublicSubnetC:
    Value: !Ref PublicSubnetC
    Description: ID of the public subnet
    Export:
      Name: subnet-pub-c

  PrivateSubnetA:
    Value: !Ref PrivateSubnetA
    Description: ID of the private subnet
    Export:
      Name: subnet-private-a

  PrivateSubnetB:
    Value: !Ref PrivateSubnetB
    Description: ID of the private subnet
    Export:
      Name: subnet-private-b

  PrivateSubnetC:
    Value: !Ref PrivateSubnetC
    Description: ID of the private subnet
    Export:
      Name: subnet-private-c