This is the new *CloudFormation Template Reference Guide*. Please update your bookmarks and links. For help getting started with CloudFormation, see the [AWS CloudFormation User Guide](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/Welcome.html).

# AWS::EC2::Instance PrivateDnsNameOptions
<a name="aws-properties-ec2-instance-privatednsnameoptions"></a>

The type of hostnames to assign to instances in the subnet at launch. For IPv4 only subnets, an instance DNS name must be based on the instance IPv4 address. For IPv6 only subnets, an instance DNS name must be based on the instance ID. For dual-stack subnets, you can specify whether DNS names use the instance IPv4 address or the instance ID. For more information, see [Amazon EC2 instance hostname types](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-naming.html) in the *Amazon Elastic Compute Cloud User Guide*.

## Syntax
<a name="aws-properties-ec2-instance-privatednsnameoptions-syntax"></a>

To declare this entity in your CloudFormation template, use the following syntax:

### JSON
<a name="aws-properties-ec2-instance-privatednsnameoptions-syntax.json"></a>

```
{
  "[EnableResourceNameDnsAAAARecord](#cfn-ec2-instance-privatednsnameoptions-enableresourcenamednsaaaarecord)" : Boolean,
  "[EnableResourceNameDnsARecord](#cfn-ec2-instance-privatednsnameoptions-enableresourcenamednsarecord)" : Boolean,
  "[HostnameType](#cfn-ec2-instance-privatednsnameoptions-hostnametype)" : String
}
```

### YAML
<a name="aws-properties-ec2-instance-privatednsnameoptions-syntax.yaml"></a>

```
  [EnableResourceNameDnsAAAARecord](#cfn-ec2-instance-privatednsnameoptions-enableresourcenamednsaaaarecord): Boolean
  [EnableResourceNameDnsARecord](#cfn-ec2-instance-privatednsnameoptions-enableresourcenamednsarecord): Boolean
  [HostnameType](#cfn-ec2-instance-privatednsnameoptions-hostnametype): String
```

## Properties
<a name="aws-properties-ec2-instance-privatednsnameoptions-properties"></a>

`EnableResourceNameDnsAAAARecord`  <a name="cfn-ec2-instance-privatednsnameoptions-enableresourcenamednsaaaarecord"></a>
Indicates whether to respond to DNS queries for instance hostnames with DNS AAAA records. For more information, see [Amazon EC2 instance hostname types](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-naming.html) in the *Amazon Elastic Compute Cloud User Guide*.  
*Required*: No  
*Type*: Boolean  
*Update requires*: [Some interruptions](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-some-interrupt)

`EnableResourceNameDnsARecord`  <a name="cfn-ec2-instance-privatednsnameoptions-enableresourcenamednsarecord"></a>
Indicates whether to respond to DNS queries for instance hostnames with DNS A records. For more information, see [Amazon EC2 instance hostname types](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-naming.html) in the *Amazon Elastic Compute Cloud User Guide*.  
*Required*: No  
*Type*: Boolean  
*Update requires*: [Some interruptions](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-some-interrupt)

`HostnameType`  <a name="cfn-ec2-instance-privatednsnameoptions-hostnametype"></a>
The type of hostnames to assign to instances in the subnet at launch. For IPv4 only subnets, an instance DNS name must be based on the instance IPv4 address. For IPv6 only subnets, an instance DNS name must be based on the instance ID. For dual-stack subnets, you can specify whether DNS names use the instance IPv4 address or the instance ID. For more information, see [Amazon EC2 instance hostname types](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-naming.html) in the *Amazon Elastic Compute Cloud User Guide*.  
*Required*: No  
*Type*: String  
*Allowed values*: `ip-name | resource-name`  
*Update requires*: [Some interruptions](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-some-interrupt)