Tukukkk

I have a CloudFormation template that creates a custom VPC.
The template creates the following resources - a VPC, an Internet Gateway, attaches the IGW to the VPC, and creates a Public Subnet.
I want to add a route (destination 0.0.0.0/0, target IGW) to the Route Table that gets created as part of the VPC.

I have read through the cloudformation documentation for routes, route tables to figure out how to do this, but to no avail.

I can use the Fn::Ref function to refer to resources or parameters that are explicitly created as part of the template, but how do I refer to resources that get created inherently with the VPC?

Any insights on how to re-use the existing route table, NACL and Security Group are much appreciated.

Thanks,

1. Don't use the default route table (see https://serverfault.com/questions/588904/aws-vpc-default-route-table-in-cloudformation)


2. You can get default security group as per https://serverfault.com/questions/544439/aws-cloudformation-vpc-default-security-group
   


3. And finally you can also get the DefaultNetworkAcl in the same as DefaultSecurityGroup above. See also https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-vpc.html)

Good job so far - you have your internet gateway, route table, and a public subnet. Now you need to create the route and attach the route table to the subnet if you haven't already done so. If you're using YAML it might look something like this:

 InternetGateway:

    Type: AWS::EC2::InternetGateway

    Properties:

      Tags:

        - Key: Name

          Value: !Ref EnvironmentName



  InternetGatewayAttachment:

    Type: AWS::EC2::VPCGatewayAttachment

    Properties:

      InternetGatewayId: !Ref InternetGateway

      VpcId: !Ref VPC



  PublicSubnet1:

    Type: AWS::EC2::Subnet

    Properties:

      VpcId: !Ref VPC

      AvailabilityZone: !Select [ 0, !GetAZs '' ]

      CidrBlock: !Ref PublicSubnet1CIDR

      MapPublicIpOnLaunch: true

      Tags:

        - Key: Name

          Value: !Sub ${EnvironmentName} Public Subnet (AZ1)



  PublicRouteTable:

    Type: AWS::EC2::RouteTable

    Properties:

      VpcId: !Ref VPC

      Tags:

        - Key: Name

          Value: !Sub ${EnvironmentName} Public Routes



  DefaultPublicRoute:

    Type: AWS::EC2::Route

    DependsOn: InternetGatewayAttachment

    Properties:

      RouteTableId: !Ref PublicRouteTable

      DestinationCidrBlock: 0.0.0.0/0

      GatewayId: !Ref InternetGateway



  PublicSubnet1RouteTableAssociation:

    Type: AWS::EC2::SubnetRouteTableAssociation

    Properties:

      RouteTableId: !Ref PublicRouteTable

      SubnetId: !Ref PublicSubnet1