cloudformation.subnet.yml

AWSTemplateFormatVersion: '2010-09-09'

Parameters:

  AvailabilityZone:
    Type: AWS::EC2::AvailabilityZone::Name
    Description: Availability zone in which to create the subnet

  Cidr:
    Type: String
    Description: IP address range which instances in this subnet will be assigned

  CreateNatGateway:
    Type: String
    Description: >
      Only for public subnets, a NAT gateway and route table can be created.
      A private subnet can then use the route table to route egress traffic to the NAT gateway.
    AllowedValues:
      - 'yes'
      - 'no'

  Name:
    Type: String
    Description: Name of subnet resources (e.g. private, servers, etc.)
    AllowedPattern: ^[a-z0-9-]*$

  RouteTableId:
    Type: String
    Description: ID of the route table which this subnet will use for routing traffic

  SubnetType:
    Type: String
    Description: >
      Is this a public or private subnet? Public subnets will get an EIP
      and can have a NAT gateway generated in them.
    AllowedValues:
      - 'public'
      - 'private'

  VpcId:
    Type: AWS::EC2::VPC::Id
    Description: ID of the VPC in which resources will be created


Conditions:

  IsPublicSubnet: !Equals [!Ref SubnetType, 'public']

  IsCreateNatGateway: !And [!Condition IsPublicSubnet, !Equals [!Ref CreateNatGateway, 'yes']]


Resources:

  Subnet:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VpcId
      AvailabilityZone: !Ref AvailabilityZone
      CidrBlock: !Ref Cidr
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: !Ref Name

  RouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref RouteTableId
      SubnetId: !Ref Subnet

  EIP:
    Type: AWS::EC2::EIP
    Condition: IsPublicSubnet
    Properties:
      Domain: vpc

  NatGateway:
    Type: AWS::EC2::NatGateway
    Condition:  IsCreateNatGateway
    Properties:
      AllocationId: !GetAtt EIP.AllocationId
      SubnetId: !Ref Subnet
      Tags:
        - Key: Name
          Value: !Ref Name

  NatRouteTable:
    Type: AWS::EC2::RouteTable
    Condition:  IsCreateNatGateway
    Properties:
      VpcId: !Ref VpcId
      Tags:
        - Key: Name
          Value: !Sub ${Name}-nat

  NatDefaultRoute:
    Type: AWS::EC2::Route
    Condition:  IsCreateNatGateway
    Properties:
      RouteTableId: !Ref NatRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NatGateway


Outputs:

  SubnetId:
    Value: !Ref Subnet

  NatRouteTableId:
    Value: !Ref NatRouteTable
    Condition: IsCreateNatGateway