Deploy AWS Public, Private Subnet & Route Table Creation & Associate Using CloudFormation

May 18, 2024

by Dheeraj Choudhary

with 535 comments

CloudFormation

Welcome back to the series of AWS Cloudformation For Beginners 👨🏻‍💻. In this blog we will be deploying Public Subnet, Private Subnet & Create Public, Private Route Tables & Associate these route tables to the subnets with help of VS Code Cloudformation Extension.

If you are a beginner and want to start your journey towards infra-as-code developer as part of your devops role buckle up 🚴‍♂️ and lets get started and understand core cloudformation concepts by implementing it…🎬

🌟Launch Public Subnet, Public Route Table & Associate🌟

Create public subnet, public route table and associate that route table to public subnet🔳 Parameters:-
✦ CustomVPC :- Using this parameter for VPC “AWS::EC2::VPC::Id” we can list existing VPC list into the account and select anyone from them. Apart from this list we can also you default value if no value is selected in the parameter.
✦ CustomInternetGateway :- Using this parameter for Internet gateway with type “String” we are setting default value for this parameter.
🔳 Resources
✦ PublicSubnet:-Specifies a subnet for a VPC. When you create each subnet, you provide the VPC ID and IPv4 CIDR block for the subnet. After you create a subnet, you can’t change its CIDR block. The size of the subnet’s IPv4 CIDR block can be the same as a VPC’s IPv4 CIDR block, or a subset of a VPC’s IPv4 CIDR block.
✦ PublicRouteTable:- Specifies a route table for a specified VPC. After you create a route table, you can add routes and associate the table with a subnet.
✦ PublicRoute:-Specifies a route in a route table within a VPC.You must specify either DestinationCidrBlock or DestinationIpv6CidrBlock, plus the ID of one of the target resources.
✦ PublicSubnetRouteTableAssociation:-Associates a subnet with a route table. The subnet and route table must be in the same VPC. This association causes traffic originating from the subnet to be routed according to the routes in the route table. A route table can be associated with multiple subnets.
🔳 Outputs: Its always a best practice to print output for your resources.
✦ outputVPC: A reference to the created VPC.
✦ outputPublicSubnets: A reference to the created Public subnet.
✦ outputPublicRouteTable: A reference to the created PublicRouteTable.
✦ outputPublicRoute: A reference to the created PublicRoute.
✦ outputPublicSubnetRouteTableAssociation: A reference to the created PublicSubnetRouteTableAssociation.

Parameters:
  CustomVPC:
    Description: Select One VPC available in your existing account
    Type: AWS::EC2::VPC::Id
    Default: "<Your VPC ID>"
  CustomInternetGateway:
    Description: Select One internet gateway available in your existing account
    Type: String
    Default: "<Your InternetGateway ID>"
Resources:
  PublicSubnet:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Select [ 0, !GetAZs '' ]
      MapPublicIpOnLaunch: true
      VpcId: !Ref CustomVPC
      CidrBlock: 10.0.0.0/26
      Tags:
        - Key: Name
          Value: PublicSubnet
  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId:  
        Ref: CustomVPC
      Tags:
      - Key: Name
        Value: PublicRouteTable
  PublicRoute:   # Public route table has direct routing to IGW:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref CustomInternetGateway  
  PublicSubnet1RouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PublicSubnet
      RouteTableId: !Ref PublicRouteTable
Outputs:
  outputVPC:
    Description: A reference to the created VPC
    Value: !Ref CustomVPC
  outputPublicSubnets:
    Description: Public subnet
    Value: !Ref PublicSubnet
  outputPublicRouteTable:
    Description: A reference to the created PublicRouteTable
    Value: !Ref PublicRouteTable
  outputPublicRoute:
    Description: A reference to the created PublicRoute
    Value: !Ref PublicRoute
  outputPublicSubnetRouteTableAssociation:
    Description: A reference to the created PublicSubnetRouteTableAssociation
    Value: !Ref PublicSubnetRouteTableAssociation

🔊 To view entire github code click here

1️⃣ Lets validate our template 👨‍💻

aws cloudformation validate-template --template-body file://<file path>

2️⃣ After successfull template verification lets create stack using our template 👨‍💻

aws cloudformation create-stack --stack-name launchpublicsubnet --template-body file://<file path>

Note:- If you are not providing default vpc id in parameter then you will have to use below command

aws cloudformation create-stack --stack-name launchpublicsubnet --template-body file://<file path> --parameters ParameterKey=CustomVPC,ParameterValue=<VPC ID>

3️⃣ Check if the stack we created via template is completed successfully 👨‍💻

aws cloudformation list-stack-resources --stack-name launchpublicsubnet

4️⃣ Describe stack and its resources to view its properties 👨‍💻

aws cloudformation describe-stacks --stack-name launchpublicsubnet

aws cloudformation describe-stack-resources --stack-name launchpublicsubnet

5️⃣ Check events for stack formation 👨‍💻

aws cloudformation describe-stack-events --stack-name launchpublicsubnet

👁‍🗨👁‍🗨 YouTube Tutorial 📽

🌟Launch Private Subnet, Private Route Table & Associate🌟

Create private subnet, private route table and associate that route table to private subnet.🔳 Parameters:-
✦ CustomVPC :- Using this parameter for VPC “AWS::EC2::VPC::Id” we can list existing VPC list into the account and select anyone from them. Apart from this list we can also you default value if no value is selected in the parameter.
🔳 Resources
✦ PrivateSubnet:-Specifies a subnet for a VPC.When you create each subnet, you provide the VPC ID and IPv4 CIDR block for the subnet. After you create a subnet, you can’t change its CIDR block. The size of the subnet’s IPv4 CIDR block can be the same as a VPC’s IPv4 CIDR block, or a subset of a VPC’s IPv4 CIDR block.
✦ PrivateRouteTable:- Specifies a route table for a specified VPC. After you create a route table, you can add routes and associate the table with a subnet.
✦ PrivateSubnetARouteTableAssociation:-Associates a subnet with a route table. The subnet and route table must be in the same VPC. This association causes traffic originating from the subnet to be routed according to the routes in the route table. A route table can be associated with multiple subnets.
🔳 Outputs: Its always a best practice to print output for your resources.
✦ outputVPC: A reference to the created VPC.
✦ outputPrivateSubnets: A reference to the created Private Subnets.
✦ outputPrivateRouteTable: A reference to the created PrivateRouteTable.
✦ outputPrivateSubnetRouteTableAssociation: A reference to the created PrivateSubnetRouteTableAssociation.

Parameters:
  CustomVPC:
    Description: Select One VPC available in your existing account
    Type: AWS::EC2::VPC::Id
    Default: <Default VPC ID>
  CustomInternetGateway:
    Description: Select One internet gateway available in your existing account
    Type: String
    Default: "igw-0f49c140e9b981dc3"
Resources:
  PrivateSubnet:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Select [ 0, !GetAZs '' ]
      MapPublicIpOnLaunch: true
      VpcId: !Ref CustomVPC
      CidrBlock: 10.0.0.64/26
      Tags:
        - Key: Name
          Value: PrivateSubnet
  PrivateRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref CustomVPC
      Tags:
      - Key: Name
        Value: PrivateRouteTable
  PrivateSubnetARouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PrivateSubnet
      RouteTableId: !Ref PrivateRouteTable
Outputs:
  outputVPC:
    Description: A reference to the created VPC
    Value: !Ref CustomVPC
  outputPrivateSubnets:
    Description: A reference to the created Private subnet
    Value: !Ref PrivateSubnet
  outputPrivateRouteTable:
    Description: A reference to the created Private Route Table
    Value: !Ref PrivateRouteTable
  outputPrivateSubnetRouteTableAssociation:
    Description: A reference to the created Private Subnet Route Table Association
    Value: !Ref PrivateSubnetARouteTableAssociation

🔊 To view entire github code click here

1️⃣ Lets validate our template 👨‍💻

aws cloudformation validate-template --template-body file://<file path>

2️⃣ After successfull template verification lets create stack using our template 👨‍💻

aws cloudformation create-stack --stack-name launchprivatesubnet --template-body file://<file path>

Note:- If you are not providing default vpc id in parameter then you will have to use below command

aws cloudformation create-stack --stack-name launchprivatesubnet --template-body file://<file path> --parameters ParameterKey=CustomVPC,ParameterValue=<VPC ID>

3️⃣ Check if the stack we created via template is completed successfully 👨‍💻

aws cloudformation list-stack-resources --stack-name launchprivatesubnet

4️⃣ Describe stack and its resources to view its properties 👨‍💻

aws cloudformation describe-stacks --stack-name launchprivatesubnet

aws cloudformation describe-stack-resources --stack-name launchprivatesubnet

5️⃣ Check events for stack formation 👨‍💻

aws cloudformation describe-stack-events --stack-name launchprivatesubnet

👁‍🗨👁‍🗨 YouTube Tutorial 📽

❗️❗️Important AWS Documentation To Be Viewed❗️❗️

⛔️ AWS::EC2::VPC
⛔️ AWS::EC2::InternetGateway
⛔️ AWS::EC2::Subnet
⛔️ AWS::EC2::RouteTable
⛔️ AWS::EC2::Route
⛔️ AWS::EC2::SubnetRouteTableAssociation
⛔️ Condition functions
⛔️ Managing route tables for your VPC

🥁🥁 Conclusion 🥁🥁

In this blog I have covered 2 usecases in which we will create
✦ Public subnet, public route table and associate that route table to public subnet.
✦ Private subnet, private route table and associate that route table to private subnet.
I have used AWS CLI command to deploy these template and trust me AWS CLI is the realtime hero and I would suggest you to get acquainted towards it. Going forward I will be releasing further parts to this CloudFormation journey

📢 Stay tuned for my next blog…..

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Author - Dheeraj Choudhary

I am an IT Professional with 11+ years of experience specializing in DevOps & Build and Release Engineering, Software configuration management in automating, build, deploy and release. I blog about AWS and DevOps on my YouTube channel, which focuses on content such as, AWS, DevOps, open source, AI-ML and AWS community activities.