Table Of Contents


User Guide

First time using the AWS CLI? See the User Guide for help getting started.

[ aws . ec2 ]



Creates a subnet in an existing 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. If you create more than one subnet in a VPC, the subnets' CIDR blocks must not overlap. The smallest IPv4 subnet (and VPC) you can create uses a /28 netmask (16 IPv4 addresses), and the largest uses a /16 netmask (65,536 IPv4 addresses).

If you've associated an IPv6 CIDR block with your VPC, you can create a subnet with an IPv6 CIDR block that uses a /64 prefix length.


AWS reserves both the first four and the last IPv4 address in each subnet's CIDR block. They're not available for use.

If you add more than one subnet to a VPC, they're set up in a star topology with a logical router in the middle.

If you launch an instance in a VPC using an Amazon EBS-backed AMI, the IP address doesn't change if you stop and restart the instance (unlike a similar instance launched outside a VPC, which gets a new IP address when restarted). It's therefore possible to have a subnet with no running instances (they're all stopped), but no remaining IP addresses available.

For more information about subnets, see Your VPC and Subnets in the Amazon Virtual Private Cloud User Guide .

See also: AWS API Documentation

See 'aws help' for descriptions of global parameters.


[--availability-zone <value>]
[--availability-zone-id <value>]
--cidr-block <value>
[--ipv6-cidr-block <value>]
--vpc-id <value>
[--dry-run | --no-dry-run]
[--cli-input-json <value>]
[--generate-cli-skeleton <value>]


--availability-zone (string)

The Availability Zone for the subnet.

Default: AWS selects one for you. If you create more than one subnet in your VPC, we may not necessarily select a different zone for each subnet.

--availability-zone-id (string)

The AZ ID of the subnet.

--cidr-block (string)

The IPv4 network range for the subnet, in CIDR notation. For example, .

--ipv6-cidr-block (string)

The IPv6 network range for the subnet, in CIDR notation. The subnet size must use a /64 prefix length.

--vpc-id (string)

The ID of the VPC.

--dry-run | --no-dry-run (boolean)

Checks whether you have the required permissions for the action, without actually making the request, and provides an error response. If you have the required permissions, the error response is DryRunOperation . Otherwise, it is UnauthorizedOperation .

--cli-input-json (string) Performs service operation based on the JSON string provided. The JSON string follows the format provided by --generate-cli-skeleton. If other arguments are provided on the command line, the CLI values will override the JSON-provided values. It is not possible to pass arbitrary binary values using a JSON-provided value as the string will be taken literally.

--generate-cli-skeleton (string) Prints a JSON skeleton to standard output without sending an API request. If provided with no value or the value input, prints a sample input JSON that can be used as an argument for --cli-input-json. If provided with the value output, it validates the command inputs and returns a sample output JSON for that command.

See 'aws help' for descriptions of global parameters.


To create a subnet

This example creates a subnet in the specified VPC with the specified IPv4 CIDR block. We recommend that you let us select an Availability Zone for you. Alternatively, you can use the --availability-zone option to specify the Availability Zone.


aws ec2 create-subnet --vpc-id vpc-a01106c2 --cidr-block


    "Subnet": {
      "VpcId": "vpc-a01106c2",
      "AvailableIpAddressCount": 251,
      "MapPublicIpOnLaunch": false,
      "DefaultForAz": false,
      "Ipv6CidrBlockAssociationSet": [],
      "State": "pending",
      "AvailabilityZone": "us-east-1a",
      "SubnetId": "subnet-2c2de375",
      "CidrBlock": "",
      "AssignIpv6AddressOnCreation": false

To create a subnet with an IPv6 CIDR block

This example creates a subnet in the specified VPC with the specified IPv4 and IPv6 CIDR blocks (from the ranges of the VPC).


aws ec2 create-subnet --vpc-id vpc-31896b55 --cidr-block --ipv6-cidr-block 2001:db8:1234:a100::/64


  "Subnet": {
      "VpcId": "vpc-31896b55",
      "AvailableIpAddressCount": 251,
      "MapPublicIpOnLaunch": false,
      "DefaultForAz": false,
      "Ipv6CidrBlockAssociationSet": [
              "Ipv6CidrBlock": "2001:db8:1234:a100::/64",
              "AssociationId": "subnet-cidr-assoc-3fe7e347",
              "Ipv6CidrBlockState": {
                  "State": "ASSOCIATING"
      "State": "pending",
      "AvailabilityZone": "ap-southeast-2a",
      "SubnetId": "subnet-5504d223",
      "CidrBlock": "",
      "AssignIpv6AddressOnCreation": false


Subnet -> (structure)

Information about the subnet.

AvailabilityZone -> (string)

The Availability Zone of the subnet.

AvailabilityZoneId -> (string)

The AZ ID of the subnet.

AvailableIpAddressCount -> (integer)

The number of unused private IPv4 addresses in the subnet. The IPv4 addresses for any stopped instances are considered unavailable.

CidrBlock -> (string)

The IPv4 CIDR block assigned to the subnet.

DefaultForAz -> (boolean)

Indicates whether this is the default subnet for the Availability Zone.

MapPublicIpOnLaunch -> (boolean)

Indicates whether instances launched in this subnet receive a public IPv4 address.

State -> (string)

The current state of the subnet.

SubnetId -> (string)

The ID of the subnet.

VpcId -> (string)

The ID of the VPC the subnet is in.

OwnerId -> (string)

The ID of the AWS account that owns the subnet.

AssignIpv6AddressOnCreation -> (boolean)

Indicates whether a network interface created in this subnet (including a network interface created by RunInstances ) receives an IPv6 address.

Ipv6CidrBlockAssociationSet -> (list)

Information about the IPv6 CIDR blocks associated with the subnet.


Describes an IPv6 CIDR block associated with a subnet.

AssociationId -> (string)

The association ID for the CIDR block.

Ipv6CidrBlock -> (string)

The IPv6 CIDR block.

Ipv6CidrBlockState -> (structure)

Information about the state of the CIDR block.

State -> (string)

The state of a CIDR block.

StatusMessage -> (string)

A message about the status of the CIDR block, if applicable.

Tags -> (list)

Any tags assigned to the subnet.


Describes a tag.

Key -> (string)

The key of the tag.

Constraints: Tag keys are case-sensitive and accept a maximum of 127 Unicode characters. May not begin with aws: .

Value -> (string)

The value of the tag.

Constraints: Tag values are case-sensitive and accept a maximum of 255 Unicode characters.

SubnetArn -> (string)

The Amazon Resource Name (ARN) of the subnet.