CloudFormation

There are two important concepts to understand when using AWS CloudFormation: templates and stacks. A template is used to describe your AWS resources and their properties. When you create a stack, AWS CloudFormation provisions the resources that are described in the template.

To learn more, view the AWS documentation on stacks and templates.

Rackspace CloudFormation Template: BaseNetwork

We help customers create custom CloudFormation templates to describe their environments. We make available a standardized CloudFormation Template, BaseNetwork, that creates the initial network and all of its necessary components. The rest of this section describes the elements that are part of the BaseNetwork CloudFormation Template and the associated components. You can download the BaseNetwork template here.

Parameters

• VPCCIDR - CIDR for the VPC

• SubnetPublicAZ1 - CIDR for Public subnet

• SubnetPublicAZ2 - CIDR for Public subnet

• SubnetPrivateAZ1 - CIDR for Private subnet

• SubnetPrivateAZ2 - CIDR for Private subnet

• InstanceTenancy - Single or Multi-Tenant Hypervisor

• Environment - Dev, Test, Prod etc.

Networking

• The CloudFormation template has two major options:

  • 2 Availability Zones with 4 Subnets

  • 3 Availability Zones with 6 Subnets

• Defaults to using CIDR: 172.18.0.0/16

  • Public Ranges

    • 172.18.0.0/22 - 1,022 Hosts - Public AZ1

    • 172.18.4.0/22 - 1,022 Hosts - Public AZ2

    • 172.18.8.0/22 - 1,022 Hosts - Public AZ3

    • 172.18.12.0/22 - 1,022 Hosts - Public AZx

    • 172.18.16.0/20 - 4,094 Hosts - Additional public (4 more public with size listed above)

  • Private Ranges

    • 172.18.32.0/21 - 2,046 Hosts - Private AZ1

    • 172.18.40.0/21 - 2,046 Hosts - Private AZ2

    • 172.18.48.0/21 - 2,046 Hosts - Private AZ3

    • 172.18.56.0/21 - 2,046 Hosts - Private AZx

    • 172.18.64.0/18 - 16,382 Hosts - - Additional private (8 more private using size above)

  • 172.18.128.0/17 - 32,766 Hosts - Special needs (16 more private using size above)

• Route Tables

  • RouteTablePublic - route table for Public subnets

  • RouteTablePrivateAZ1 - route table for Subnet Private AZ1

  • RouteTablePrivateAZ2 - route table for Subnet Private AZ2

• Default Gateways

  • Internet Gateway (IGW) - Default GW for the Public Subnets

  • ASGNatAZ1 Instance ID - Default GW for Subnet Private AZ1

  • ASGNatAZ2 Instance ID - Default GW for Subnet Private AZ2

  • ASGNatAZ3 Instance ID - Default GW for Subnet Private AZ3 (if necessary)

HA NAT

• High Availability NAT gateways get created in the public subnets (1 per AZ)

  • NatAZ1

  • NatAZ2

  • NatAZ3 (if necessary)

Tags

• Service Provider - “Rackspace”

• Environment - from Parameter Environment

• Name - Resource name (e.g. IGWBase, SubnetPublicAZ2)

Outputs

• outputVPCID

• outputSubnetPublicAZ1

• outputSubnetPublicAZ2

• outputSubnetPublicAZ3 (if necessary)

• outputSubnetPrivateAZ1

• outputSubnetPrivateAZ2

• outputSubnetPrivateAZ3 (if necessary)