03. VPC and Internet Gateway

Note: Based on student feedback, we've broken up some of the longer video tutorials in this lesson into smaller chunks, so that students may digest and process the content more easily.

ND9991 C02 L03 A03-1 VPC And Internet Gateway P1

ND9991 C02 L03 A03-2 VPC And Internet Gateway P2

ND9991 C02 L03 A03-2 VPC And Internet Gateway P3

#### Connecting VPC's & Internet Gateways

It's important to note when connecting an Internet Gateway to a VPC, we need to define an additional resource called InternetGatewayAttachment. This attachment references both the VPC and the InternetGateway. Here is the syntax for the following connection:

Type: AWS::EC2::VPCGatewayAttachment
Properties: 
  InternetGatewayId: String
  VpcId: String
  VpnGatewayId: String

### Don't hard-code parameters

Avoid hard coding parameter values. Instead, use a separate parameter file to store parameter values. Note that the parameter file should be in .json format, as .yml format is not yet supported for the parameter file.

Here is an example parameters file from network-parameters.json which is holding key-value pairs for the Environment & VpcCiIDR.

[
    {
        "ParameterKey": "EnvironmentName",
        "ParameterValue": "UdacityProject"
    },
    {
        "ParameterKey": "VpcCIDR",
        "ParameterValue": "10.0.0.0/16"
    }
]


#### Setting Parameters

Parameters should be declared above your Resources:

Parameters:
# whatever you consider a changing value, put it as a parameter instead of hard-coding it into your script
Resources:

and should follow the general format of: 

Parameters:
  ParameterLogicalID:
    Type: DataType
    ParameterProperty: value

Here we set the EnvironmentName parameter in our sample code from the video:

Parameters:
    EnvironmentName:
        Description: An Environment name that will be prefixed to resources
        Type: String

#### Default Parameters

You can also provide default values for parameters in case one was not passed in. In this example you can see that VpcCIDR has a default value of 10.0.0.0/16.

Parameters:
    EnvironmentName:
        Description: An Environment name that will be prefixed to resources
        Type: String

    VpcCIDR:
        Description: Please enter the IP range (CIDR notation) for this
        Type: String
        Default: 10.0.0.0/16


#### Calling CloudFormation

When calling AWS CloudFormation, you’ll pass in the name of the .yml file as well as the name of the parameter file as parameters to the CloudFormation call.

For example:

aws cloudformation create-stack --stack-name MyStack --template-body file://MyCloudformationScript.yml  --parameters file://MyEnvironmentVariables.json
  • Note that CloudFormation knows to create the resources in order, based on their dependencies (VPC and InternetGateway, before creating the InternetGatewayAttachment).

#### Further Resources

Next Concept