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::VPCCidrBlock
<a name="aws-resource-ec2-vpccidrblock"></a>

Associates a CIDR block with your VPC.

A VPC must have an associated IPv4 CIDR block. You can optionally associate additional IPv4 CIDR blocks with a VPC. You can optionally associate an IPv6 CIDR block with a VPC. You can request an Amazon-provided IPv6 CIDR block from Amazon's pool of IPv6 addresses, or an IPv6 CIDR block from an IPv6 address pool that you provisioned through bring your own IP addresses (BYOIP).

For more information, see [VPC CIDR blocks](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-cidr-blocks.html) in the *Amazon VPC User Guide*.

## Syntax
<a name="aws-resource-ec2-vpccidrblock-syntax"></a>

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

### JSON
<a name="aws-resource-ec2-vpccidrblock-syntax.json"></a>

```
{
  "Type" : "AWS::EC2::VPCCidrBlock",
  "Properties" : {
      "[AmazonProvidedIpv6CidrBlock](#cfn-ec2-vpccidrblock-amazonprovidedipv6cidrblock)" : Boolean,
      "[CidrBlock](#cfn-ec2-vpccidrblock-cidrblock)" : String,
      "[Ipv4IpamPoolId](#cfn-ec2-vpccidrblock-ipv4ipampoolid)" : String,
      "[Ipv4NetmaskLength](#cfn-ec2-vpccidrblock-ipv4netmasklength)" : Integer,
      "[Ipv6CidrBlock](#cfn-ec2-vpccidrblock-ipv6cidrblock)" : String,
      "[Ipv6CidrBlockNetworkBorderGroup](#cfn-ec2-vpccidrblock-ipv6cidrblocknetworkbordergroup)" : String,
      "[Ipv6IpamPoolId](#cfn-ec2-vpccidrblock-ipv6ipampoolid)" : String,
      "[Ipv6NetmaskLength](#cfn-ec2-vpccidrblock-ipv6netmasklength)" : Integer,
      "[Ipv6Pool](#cfn-ec2-vpccidrblock-ipv6pool)" : String,
      "[VpcId](#cfn-ec2-vpccidrblock-vpcid)" : String
    }
}
```

### YAML
<a name="aws-resource-ec2-vpccidrblock-syntax.yaml"></a>

```
Type: AWS::EC2::VPCCidrBlock
Properties:
  [AmazonProvidedIpv6CidrBlock](#cfn-ec2-vpccidrblock-amazonprovidedipv6cidrblock): Boolean
  [CidrBlock](#cfn-ec2-vpccidrblock-cidrblock): String
  [Ipv4IpamPoolId](#cfn-ec2-vpccidrblock-ipv4ipampoolid): String
  [Ipv4NetmaskLength](#cfn-ec2-vpccidrblock-ipv4netmasklength): Integer
  [Ipv6CidrBlock](#cfn-ec2-vpccidrblock-ipv6cidrblock): String
  [Ipv6CidrBlockNetworkBorderGroup](#cfn-ec2-vpccidrblock-ipv6cidrblocknetworkbordergroup): String
  [Ipv6IpamPoolId](#cfn-ec2-vpccidrblock-ipv6ipampoolid): String
  [Ipv6NetmaskLength](#cfn-ec2-vpccidrblock-ipv6netmasklength): Integer
  [Ipv6Pool](#cfn-ec2-vpccidrblock-ipv6pool): String
  [VpcId](#cfn-ec2-vpccidrblock-vpcid): String
```

## Properties
<a name="aws-resource-ec2-vpccidrblock-properties"></a>

`AmazonProvidedIpv6CidrBlock`  <a name="cfn-ec2-vpccidrblock-amazonprovidedipv6cidrblock"></a>
Requests an Amazon-provided IPv6 CIDR block with a /56 prefix length for the VPC. You cannot specify the range of IPv6 addresses or the size of the CIDR block.  
*Required*: No  
*Type*: Boolean  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`CidrBlock`  <a name="cfn-ec2-vpccidrblock-cidrblock"></a>
An IPv4 CIDR block to associate with the VPC.  
*Required*: No  
*Type*: String  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`Ipv4IpamPoolId`  <a name="cfn-ec2-vpccidrblock-ipv4ipampoolid"></a>
Associate a CIDR allocated from an IPv4 IPAM pool to a VPC. For more information about Amazon VPC IP Address Manager (IPAM), see [What is IPAM?](https://docs.aws.amazon.com//vpc/latest/ipam/what-is-it-ipam.html) in the *Amazon VPC IPAM User Guide*.  
*Required*: No  
*Type*: String  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`Ipv4NetmaskLength`  <a name="cfn-ec2-vpccidrblock-ipv4netmasklength"></a>
The netmask length of the IPv4 CIDR you would like to associate from an Amazon VPC IP Address Manager (IPAM) pool. For more information about IPAM, see [What is IPAM?](https://docs.aws.amazon.com//vpc/latest/ipam/what-is-it-ipam.html) in the *Amazon VPC IPAM User Guide*.   
*Required*: No  
*Type*: Integer  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`Ipv6CidrBlock`  <a name="cfn-ec2-vpccidrblock-ipv6cidrblock"></a>
An IPv6 CIDR block from the IPv6 address pool. You must also specify `Ipv6Pool` in the request.  
To let Amazon choose the IPv6 CIDR block for you, omit this parameter.  
*Required*: No  
*Type*: String  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`Ipv6CidrBlockNetworkBorderGroup`  <a name="cfn-ec2-vpccidrblock-ipv6cidrblocknetworkbordergroup"></a>
The name of the location from which we advertise the IPV6 CIDR block. Use this parameter to limit the CIDR block to this location.  
 You must set `AmazonProvidedIpv6CidrBlock` to `true` to use this parameter.  
 You can have one IPv6 CIDR block association per network border group.  
*Required*: No  
*Type*: String  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`Ipv6IpamPoolId`  <a name="cfn-ec2-vpccidrblock-ipv6ipampoolid"></a>
Associates a CIDR allocated from an IPv6 IPAM pool to a VPC. For more information about Amazon VPC IP Address Manager (IPAM), see [What is IPAM?](https://docs.aws.amazon.com//vpc/latest/ipam/what-is-it-ipam.html) in the *Amazon VPC IPAM User Guide*.  
*Required*: No  
*Type*: String  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`Ipv6NetmaskLength`  <a name="cfn-ec2-vpccidrblock-ipv6netmasklength"></a>
The netmask length of the IPv6 CIDR you would like to associate from an Amazon VPC IP Address Manager (IPAM) pool. For more information about IPAM, see [What is IPAM?](https://docs.aws.amazon.com//vpc/latest/ipam/what-is-it-ipam.html) in the *Amazon VPC IPAM User Guide*.   
*Required*: No  
*Type*: Integer  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`Ipv6Pool`  <a name="cfn-ec2-vpccidrblock-ipv6pool"></a>
The ID of an IPv6 address pool from which to allocate the IPv6 CIDR block.  
*Required*: No  
*Type*: String  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

`VpcId`  <a name="cfn-ec2-vpccidrblock-vpcid"></a>
The ID of the VPC.  
*Required*: Yes  
*Type*: String  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

## Return values
<a name="aws-resource-ec2-vpccidrblock-return-values"></a>

### Ref
<a name="aws-resource-ec2-vpccidrblock-return-values-ref"></a>

When you pass the logical ID of this resource to the intrinsic `Ref` function, `Ref` returns the association ID for the VPC CIDR block.

For more information about using the `Ref` function, see [https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/intrinsic-function-reference-ref.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/intrinsic-function-reference-ref.html).

### Fn::GetAtt
<a name="aws-resource-ec2-vpccidrblock-return-values-fn--getatt"></a>

#### 
<a name="aws-resource-ec2-vpccidrblock-return-values-fn--getatt-fn--getatt"></a>

`IpSource`  <a name="IpSource-fn::getatt"></a>
The source that allocated the IP address space. `byoip` or `amazon` indicates public IP address space allocated by Amazon or space that you have allocated with Bring your own IP (BYOIP). `none` indicates private space.

`Ipv6AddressAttribute`  <a name="Ipv6AddressAttribute-fn::getatt"></a>
Public IPv6 addresses are those advertised on the internet from AWS. Private IP addresses are not and cannot be advertised on the internet from AWS.

## Examples
<a name="aws-resource-ec2-vpccidrblock--examples"></a>



**Topics**
+ [Associate an Amazon-provided IPv6 CIDR block](#aws-resource-ec2-vpccidrblock--examples--Associate_an_Amazon-provided_IPv6_CIDR_block)
+ [Associate an IPv4 CIDR block and an Amazon-provided IPv6 CIDR block](#aws-resource-ec2-vpccidrblock--examples--Associate_an_IPv4_CIDR_block_and_an_Amazon-provided_IPv6_CIDR_block)

### Associate an Amazon-provided IPv6 CIDR block
<a name="aws-resource-ec2-vpccidrblock--examples--Associate_an_Amazon-provided_IPv6_CIDR_block"></a>

The following example associates an Amazon-provided IPv6 CIDR block (with a prefix length of /56) with the TestVPCIpv6 VPC. 

#### JSON
<a name="aws-resource-ec2-vpccidrblock--examples--Associate_an_Amazon-provided_IPv6_CIDR_block--json"></a>

```
"Ipv6VPCCidrBlock": {
   "Type": "AWS::EC2::VPCCidrBlock",
   "Properties": {
      "AmazonProvidedIpv6CidrBlock": true,
      "VpcId": { "Ref" : "TestVPCIpv6" }
   }
}
```

#### YAML
<a name="aws-resource-ec2-vpccidrblock--examples--Associate_an_Amazon-provided_IPv6_CIDR_block--yaml"></a>

```
Ipv6VPCCidrBlock:
   Type: AWS::EC2::VPCCidrBlock
   Properties:
      AmazonProvidedIpv6CidrBlock: true
      VpcId: !Ref TestVPCIpv6
```

### Associate an IPv4 CIDR block and an Amazon-provided IPv6 CIDR block
<a name="aws-resource-ec2-vpccidrblock--examples--Associate_an_IPv4_CIDR_block_and_an_Amazon-provided_IPv6_CIDR_block"></a>

The following example associates an IPv4 CIDR block and an Amazon-provided IPv6 CIDR block with a VPC. It also outputs the list of IPv4 CIDR block association IDs and IPv6 CIDR blocks that are associated with the VPC. 

#### JSON
<a name="aws-resource-ec2-vpccidrblock--examples--Associate_an_IPv4_CIDR_block_and_an_Amazon-provided_IPv6_CIDR_block--json"></a>

```
{
    "Resources": {
        "VPC": {
            "Type": "AWS::EC2::VPC",
            "Properties": {
                "CidrBlock": "10.0.0.0/24"
            }
        },
        "VpcCidrBlock": {
            "Type": "AWS::EC2::VPCCidrBlock",
            "Properties": {
                "VpcId": {
                    "Ref": "VPC"
                },
                "CidrBlock": "192.0.0.0/24"
            }
        },
        "VpcCidrBlockIpv6": {
            "Type": "AWS::EC2::VPCCidrBlock",
            "Properties": {
                "VpcId": {
                    "Ref": "VPC"
                },
                "AmazonProvidedIpv6CidrBlock": true
            }
        }
    },
    "Outputs": {
        "VpcId": {
            "Value": {
                "Ref": "VPC"
            }
        },
        "PrimaryCidrBlock": {
            "Value": {
                "Fn::GetAtt": [
                    "VPC",
                    "CidrBlock"
                ]
            }
        },
        "Ipv6CidrBlock": {
            "Value": {
                "Fn::Select": [
                    0,
                    {
                        "Fn::GetAtt": [
                            "VPC",
                            "Ipv6CidrBlocks"
                        ]
                    }
                ]
            }
        },
        "CidrBlockAssociation": {
            "Value": {
                "Fn::Select": [
                    0,
                    {
                        "Fn::GetAtt": [
                            "VPC",
                            "CidrBlockAssociations"
                        ]
                    }
                ]
            }
        }
    }
}
```

#### YAML
<a name="aws-resource-ec2-vpccidrblock--examples--Associate_an_IPv4_CIDR_block_and_an_Amazon-provided_IPv6_CIDR_block--yaml"></a>

```
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/24
  VpcCidrBlock:
    Type: AWS::EC2::VPCCidrBlock
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 192.0.0.0/24
  VpcCidrBlockIpv6:
    Type: AWS::EC2::VPCCidrBlock
    Properties:
      VpcId: !Ref VPC
      AmazonProvidedIpv6CidrBlock: true

Outputs:
  VpcId:
    Value: !Ref VPC
  PrimaryCidrBlock:
    Value: !GetAtt VPC.CidrBlock
  Ipv6CidrBlock:
    Value: !Select [ 0, !GetAtt VPC.Ipv6CidrBlocks ]
  CidrBlockAssociation:
    Value: !Select [ 0, !GetAtt VPC.CidrBlockAssociations ]
```