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Data Source: aws_subnet#

Provides information about a subnet.

This data source can be used when a module accepts a subnet ID as an input variable and needs to, for example, determine the ID of the VPC that owns the subnet.

Example usage#

Specific examples#

The following example shows how to accept a subnet ID as a variable and use this data source to obtain the data necessary to create a security group that allows connections from hosts in that subnet.

variable "subnet_id" {}

data "aws_subnet" "selected" {
  id = var.subnet_id
}

resource "aws_security_group" "subnet" {
  vpc_id = data.aws_subnet.selected.vpc_id

  ingress {
    cidr_blocks = [data.aws_subnet.selected.cidr_block]
    from_port   = 80
    to_port     = 80
    protocol    = "tcp"
  }
}

If you want to match against tag Name, use:

data "aws_subnet" "selected" {
  filter {
    name   = "tag:Name"
    values = ["yakdriver"]
  }
}

Argument reference#

The arguments of this data source act as filters for querying the available subnets in the current project within the current region.

~> Note The given filters must exactly match the resource whose data will be exported as attributes.

The following arguments are optional:

  • availability_zone - (Optional, String) The availability zone where the subnet must reside.

  • default_for_az - (Optional, Boolean) Indicates whether the desired subnet must be the default subnet for its associated availability zone.

    • Default value: false

    ~> Note Setting this argument to false does not actually filter by it not being the default, because Terraform cannot distinguish between false and "not set".

  • filter - (Optional, Block) One or more name/value pairs to use as filters.

  • tags - (Optional, Map of strings) Key-value pairs. Must exactly match pairs on the required resource.
  • vpc_id - (Optional, String) The ID of the VPC that owns the desired subnet.

filter#

  • name - (Required, String) The name of the filter.
    • Constraints: Filter names are case-sensitive
  • values - (Required, List of strings) One or more filter values.
    • Constraints: Filter values are case-sensitive

Attribute reference#

Supported attributes#

In addition to all arguments above, the following attribute is exported:

  • available_ip_address_count - (Integer) The number of remaining available IPv4 addresses in the subnet.
  • cidr_block - (String) The IPv4 CIDR block for the subnet.
  • map_public_ip_on_launch - (Boolean) Indicates whether public IP addresses will be associated with instances created in this subnet. Addresses are associated only if there are available allocated Elastic IP addresses.
  • state - (String) The state that the desired subnet must have.

Unsupported attributes#

~> Note These attributes may be present in the terraform.tfstate file, but they have preset values and cannot be specified in configuration files.

The following attributes are not currently supported:

arn, assign_ipv6_address_on_creation, availability_zone_id, customer_owned_ipv4_pool, enable_dns64, enable_resource_name_dns_aaaa_record_on_launch, enable_resource_name_dns_a_record_on_launch, ipv6_cidr_block, ipv6_cidr_block_association_id, ipv6_native, map_customer_owned_ip_on_launch, outpost_arn, owner_id, private_dns_hostname_type_on_launch.