Terraform: Get Default VPC ID (Easy Methods)

• Introduction
• Step-by-Step Guide
• Code Example
• Additional Notes
• Summary
• Conclusion
• References

Managing your default Virtual Private Cloud (VPC) in Amazon Web Services (AWS) is essential for controlling your cloud infrastructure. This guide provides a practical approach to interacting with your default VPC using Terraform, enabling you to manage and reference it effectively for your AWS resources.

1. Understand Default VPCs: AWS accounts created after December 4, 2013, automatically have a default VPC in each region.

2. Import Existing Default VPC: You can import your existing default VPC into Terraform management using its VPC ID.

   terraform import aws_default_vpc.example vpc-1234567890abcdef0

3. Data Source for VPC Information: Use the aws_vpc data source to fetch information about your VPCs.

   data "aws_vpc" "default" {
     default = true
   }

4. Accessing VPC ID: Retrieve the ID of the default VPC using data.aws_vpc.default.id.

   output "default_vpc_id" {
     value = data.aws_vpc.default.id
   }

5. Using VPC ID with Other Resources: Reference the default VPC ID when configuring resources like EC2 instances or subnets.

   resource "aws_instance" "example" {
     # ... other configurations
     subnet_id = data.aws_subnet.default.id 
     vpc_security_group_ids = [aws_security_group.default.id]
   }

6. Finding Subnets in the Default VPC: Use the aws_subnets data source with filters to target subnets within the default VPC.

   data "aws_subnets" "default" {
     filter {
       name   = "vpc-id"
       values = [data.aws_vpc.default.id]
     }
   }

7. Retrieving Subnet IDs: Access the list of subnet IDs within the default VPC using data.aws_subnets.default.ids.

   output "subnet_ids" {
     value = data.aws_subnets.default.ids
   }

Remember to replace placeholder values like vpc-1234567890abcdef0 with your actual VPC ID.

This Terraform code configures the AWS provider and retrieves information about the default VPC, including its ID and subnet IDs. It then demonstrates creating a security group that allows SSH access and launching an EC2 instance within the default VPC using the retrieved subnet and security group. Remember to replace placeholder values with your own and customize the configuration as needed.

# Configure the AWS Provider
terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 4.0"
    }
  }
}

# Get the default VPC
data "aws_vpc" "default" {
  default = true
}

# Output the default VPC ID
output "default_vpc_id" {
  value = data.aws_vpc.default.id
}

# Find subnets in the default VPC
data "aws_subnets" "default" {
  filter {
    name   = "vpc-id"
    values = [data.aws_vpc.default.id]
  }
}

# Output the subnet IDs
output "subnet_ids" {
  value = data.aws_subnets.default.ids
}

# Create a security group in the default VPC (example)
resource "aws_security_group" "default" {
  name   = "default_sg"
  vpc_id = data.aws_vpc.default.id

  ingress {
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

# Launch an EC2 instance in the default VPC (example)
resource "aws_instance" "example" {
  ami           = "ami-0c55b159c9e670235" # Replace with your desired AMI
  instance_type = "t2.micro"

  # Use the first subnet ID from the list
  subnet_id              = element(data.aws_subnets.default.ids, 0)
  vpc_security_group_ids = [aws_security_group.default.id]
}

Explanation:

1. Provider Configuration: The code starts by configuring the AWS provider.
2. Data Source for Default VPC: It uses the aws_vpc data source with default = true to fetch information about the default VPC.
3. Output VPC ID: The output block named "default_vpc_id" displays the ID of the default VPC.
4. Data Source for Subnets: The aws_subnets data source is used with a filter to retrieve subnets associated with the default VPC.
5. Output Subnet IDs: The "subnet_ids" output block displays the list of subnet IDs found within the default VPC.
6. Security Group (Example): A basic security group is created within the default VPC, allowing SSH access.
7. EC2 Instance (Example): An EC2 instance is launched within the default VPC. It uses the first subnet ID from the retrieved list and associates the security group created earlier.

To Use:

1. Save: Save the code as a .tf file (e.g., main.tf).
2. Initialize: Run terraform init to initialize the Terraform working directory.
3. Apply: Run terraform apply to create the resources.

Important:

• Replace placeholder values like AMI ID with your actual values.
• This code assumes you have a default VPC available. If you don't, you'll need to create one first.
• The EC2 instance and security group examples are basic and can be customized further based on your requirements.

General Considerations:

• Default VPC Limitations: Default VPCs come with pre-configured settings that might not be ideal for all use cases. Consider their limitations before heavily relying on them for production environments.
• Customization: While you can import and manage your default VPC with Terraform, you cannot change its default settings like DNS resolution and DHCP options.
• Alternative: For greater control and customization, consider creating and managing a dedicated VPC instead of relying solely on the default one.

Security Best Practices:

• Security Groups: The provided security group example is very permissive. Always configure security groups with the principle of least privilege, allowing only necessary traffic.
• Network Access Control Lists (NACLs): Consider using NACLs in addition to security groups for an extra layer of network security at the subnet level.

Terraform Tips:

• Modularity: For larger infrastructures, organize your Terraform code into modules to improve reusability and maintainability. You can create a module for managing your default VPC and its resources.
• State Management: Use a remote backend for Terraform state to enable collaboration and prevent state corruption.
• Validation: Utilize Terraform's validation features, like terraform validate and terraform plan, to catch errors early in the development process.

Beyond the Basics:

• VPC Peering: Explore VPC peering to connect your default VPC with other VPCs in your account or different accounts.
• Transit Gateway: For complex network topologies with multiple VPCs, consider using a Transit Gateway to simplify connectivity.
• Infrastructure as Code: Embrace Infrastructure as Code (IaC) principles by managing all aspects of your AWS infrastructure, including networking, with Terraform.

By understanding these additional notes and exploring the provided resources, you can effectively manage your default VPC and build robust and secure AWS infrastructure using Terraform.

This guide provides a concise overview of managing default VPCs in AWS using Terraform.

Key Points:

• Automatic Creation: AWS accounts created after December 4, 2013, automatically receive a default VPC in each region.
• Importing Existing VPCs: Import your existing default VPC into Terraform using its ID with terraform import.
• Data Source for Information: Utilize the aws_vpc data source with default = true to retrieve information about your default VPC.
• Accessing VPC ID: Access the default VPC ID using data.aws_vpc.default.id.
• Resource Configuration: Reference the default VPC ID when configuring resources like EC2 instances or subnets.
• Finding Subnets: Use the aws_subnets data source with filters to locate subnets within the default VPC.
• Retrieving Subnet IDs: Access the list of subnet IDs within the default VPC using data.aws_subnets.default.ids.

Remember: Replace placeholder values in the provided code snippets with your actual VPC and resource IDs.

Effectively managing your default VPC in AWS is crucial for a well-structured and secure cloud infrastructure. By leveraging Terraform's capabilities, you can seamlessly integrate your default VPC management into your IaC workflows. Remember to replace placeholder values with your specific details and tailor the provided examples to your exact requirements. By following the outlined steps and considering the additional notes, you can confidently manage your default VPC and build robust, scalable, and secure applications on AWS.

• amazon web services - How to get the default vpc id with terraform ... | Mar 10, 2020 ... I am trying to get the vpc_id of default vpc in my aws account using terraform. This is what I tried but it gives an error: Error: Invalid data source.
• Getting the vpc_id of the default, or the only one VPC - AWS ... | Dear Colleagues, Sorry for a probable FAQ, but the solutions I’ve been able to find on the Internet don’t work for me. I want to avoid setting the VPC ID in my Terraform files and just want Terraform to use the only existing VPC in an AWS region. However some resources require the vpc_id, so I’ve tried variants of the following: data "aws_vpc" "default" { default = tru...
• amazon web services - How to use the VPC id and subnets id ... | Aug 29, 2018 ... Now I have a new Terraform plan (let's call this Plan B ) where I need to launch an EC2 instance. For this I need to fetch the VPC, subnet ids ...
• Getting the default vpc id | So I'm very new to terraform and wondering how the following can be done. If I want to create an ec2 instance in the default vpc how do I then refer to the ...
• Get list of all subnets in default VPC : r/Terraform | Posted by u/jaide1 - 5 votes and 6 comments
• Get VPC information and subnets - KISPHP | Mar 26, 2022 ... ... vpc-id" values = [data.aws_vpc.default.id] } } output "first_subnet_id" { value = sort(data.aws_subnets.all.ids)[0] }. Terraform. Copy. Get ...
• Terraform - How to get subnet id from vpc module : r/Terraform | Posted by u/Playful-Mud-9218 - 1 vote and 8 comments
• aws_instance fail with VPCIdNotSpecified even when ... | Trying to create an EC2 instance on a non-default VPC fails even when including vpc_security_group_ids Terraform Version $ terraform -v Terraform v0.9.5 Affected Resource(s) aws_instance Terraform ...
• How Do I Retrieve VPC Names Via Terraform? // Taccoform | Overview At some point in your AWS and Terraform journey, you may need the names of the VPCs in a given AWS region. You’d normally look to use a data source lookup, but the name field is not exposed as an attribute for aws_vpcs. Here’s a quick way to get those VPC names. Lesson You will still need to use the aws_vpcs data source to get a list of all the VPC IDs in a given region: