# Prefix delegation for Amazon EC2 network interfaces
You can assign a private IPv4 or IPv6 CIDR range, either automatically or manually, to your network interfaces. By assigning prefixes, you scale and simplify the management of applications, including container and networking applications that require multiple IP addresses on an instance. For more information about IPv4 and IPv6 addresses, see [Amazon EC2 instance IP addressing](using-instance-addressing.md).
The following assignment options are available:
+ **Automatic assignment** — AWS chooses the prefix and assigns it to your network interface. If the subnet for the network interface has a subnet CIDR reservation of type `prefix`, we select the prefixes from the subnet CIDR reservation. Otherwise, we select them from the subnet CIDR range.
+ **Manual assignment** — You specify the prefix and AWS verifies that it is not already assigned to other resources before assigning it to your network interface.
Assigning prefixes has the following benefits:
+ Increased IP addresses on a network interface — When you use a prefix, you assign a block of IP addresses as opposed to individual IP addresses. This increases the number of IP addresses for a network interface.
+ Simplified VPC management for containers — In container applications, each container requires a unique IP address. Assigning prefixes to your instance simplifies the management of your VPCs, as you can launch and terminate containers without having to call Amazon EC2 APIs for individual IP assignments.
**Contents**
+ [Basics](#ec2-prefix-basics)
+ [Considerations](#prefix-limit)
+ [Manage prefixes](work-with-prefixes.md)
+ [Assign prefixes during network interface creation](work-with-prefixes.md#assign-auto-creation)
+ [Assign prefixes to an existing network interface](work-with-prefixes.md#assign-auto-existing)
+ [Remove prefixes from your network interfaces](work-with-prefixes.md#unassign-prefix)
## Basics
+ You can assign a prefix to new or existing network interfaces.
+ To use prefixes, you assign a prefix to your network interface, attach the network interface to your instance, and then configure your operating system.
+ When you choose the option to specify a prefix, the prefix must meet the following requirements:
+ The IPv4 prefix that you can specify is `/28`.
+ The IPv6 prefix that you can specify is `/80`.
+ The prefix is in the subnet CIDR of the network interface, and does not overlap with other prefixes or IP addresses assigned to existing resources in the subnet.
+ You can assign a prefix to the primary or secondary network interface.
+ You can assign an Elastic IP address to a network interface that has a prefix assigned to it.
+ You can also assign an Elastic IP address to the IP address part of the assigned prefix.
+ We resolve the private DNS host name of an instance to the primary private IPv4 address.
+ We assign each private IPv4 address for a network interface, including those from prefixes, using the following format:
+ `us-east-1` Region
```
ip-private-ipv4-address.ec2.internal
```
+ All other Regions
```
ip-private-ipv4-address.region.compute.internal
```
## Considerations
Take the following into consideration when you use prefixes:
+ Network interfaces with prefixes are supported with [Nitro-based instances](instance-types.md#instance-hypervisor-type).
+ Prefixes for network interfaces must use IPv6 addresses or private IPv4 addresses.
+ The maximum number of IP addresses that you can assign to a network interface depends on the instance type. Each prefix that you assign to a network interface counts as one IP address. For example, a `c5.large` instance has a limit of `10` IPv4 addresses per network interface. Each network interface for this instance has a primary IPv4 address. If a network interface has no secondary IPv4 addresses, you can assign up to 9 prefixes to the network interface. For each additional IPv4 address that you assign to a network interface, you can assign one less prefix to the network interface. For more information, see [Maximum IP addresses per network interface](AvailableIpPerENI.md).
+ Prefixes are included in source/destination checks.
+ You must configure your operating system to work with network interfaces with prefixes. Note the following:
+ Some Amazon Linux AMIs contain additional scripts installed by AWS, known as `ec2-net-utils`. These scripts optionally automate the configuration of your network interfaces. They are for use only on Amazon Linux.
+ For containers, you can use a Container Network Interface (CNI) for the Kubernetes plug-in, or `dockerd` if you use Docker to manage your containers.
# Manage prefixes for your network interfaces
When you assign prefixes to a network interface, you can choose whether to let us automatically assign the prefixes or you can specify custom prefixes. If you let us automatically assign prefixes and the subnet for the network interface has a subnet CIDR reservation of type `prefix`, we select the prefixes from the subnet CIDR reservation. Otherwise, we select them from the subnet CIDR range.
**Topics**
+ [Assign prefixes during network interface creation](#assign-auto-creation)
+ [Assign prefixes to an existing network interface](#assign-auto-existing)
+ [Remove prefixes from your network interfaces](#unassign-prefix)
## Assign prefixes during network interface creation
You can assign automatic or custom prefixes when you create a network interface.
------
#### [ Console ]
**To assign automatic prefixes during network interface creation**
1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).
1. In the navigation pane, choose **Network Interfaces**.
1. Choose **Create network interface**.
1. Enter a description for the network interface, select the subnet in which to create the network interface, and configure the private IPv4 and IPv6 addresses.
1. Expand **Advanced settings**.
1. For **IPv4 prefix delegation** do one of the following:
+ To automatically assign an IPv4 prefix, choose **Auto-assign**. For **Number of IPv4 prefixes**, enter the number of prefixes to assign.
+ To assign a specific IPv4 prefix, choose **Custom**. Choose **Add new prefix** and enter the prefix.
1. For **IPv6 prefix delegation** do one of the following:
+ To automatically assign an IPv6 prefix, choose **Auto-assign**. For **Number of IPv6 prefixes**, enter the number of prefixes to assign.
+ To assign a specific IPv6 prefix, choose **Custom**. Choose **Add new prefix** and enter the prefix.
**Note**
**IPv6 prefix delegation** appears only if the selected subnet is enabled for IPv6.
1. Select the security groups to associate with the network interface and assign resource tags if needed.
1. Choose **Create network interface**.
------
#### [ AWS CLI ]
**To assign automatic IPv4 prefixes during network interface creation**
Use the [create-network-interface](https://docs.aws.amazon.com/cli/latest/reference/ec2/create-network-interface.html) command and set `--ipv4-prefix-count` to the number of IPv4 prefixes for AWS to assign. In the following example, AWS assigns one IPv4 prefix.
```
aws ec2 create-network-interface \
--subnet-id subnet-047cfed18eEXAMPLE \
--description "IPv4 automatic example" \
--ipv4-prefix-count 1
```
**To assign specific IPv4 prefixes during network interface creation**
Use the [create-network-interface](https://docs.aws.amazon.com/cli/latest/reference/ec2/create-network-interface.html) command and set `--ipv4-prefixes` to the prefixes. AWS selects IPv4 addresses from this range. In the following example, the prefix CIDR is 10.0.0.208/28.
```
aws ec2 create-network-interface \
--subnet-id subnet-047cfed18eEXAMPLE \
--description "IPv4 manual example" \
--ipv4-prefixes Ipv4Prefix=10.0.0.208/28
```
**To assign automatic IPv6 prefixes during network interface creation**
Use the [create-network-interface](https://docs.aws.amazon.com/cli/latest/reference/ec2/create-network-interface.html) command and set `--ipv6-prefix-count` to the number of IPv6 prefixes for AWS to assign. In the following example, AWS assigns one IPv6 prefix.
```
aws ec2 create-network-interface \
--subnet-id subnet-047cfed18eEXAMPLE \
--description "IPv6 automatic example" \
--ipv6-prefix-count 1
```
**To assign specific IPv6 prefixes during network interface creation**
Use the [create-network-interface](https://docs.aws.amazon.com/cli/latest/reference/ec2/create-network-interface.html) command and set `--ipv6-prefixes` to the prefixes. AWS selects IPv6 addresses from this range. In the following example, the prefix CIDR is 2600:1f13:fc2:a700:1768::/80.
```
aws ec2 create-network-interface \
--subnet-id subnet-047cfed18eEXAMPLE \
--description "IPv6 manual example" \
--ipv6-prefixes Ipv6Prefix=2600:1f13:fc2:a700:1768::/80
```
------
#### [ PowerShell ]
**To assign automatic IPv4 prefixes during network interface creation**
Use the [New-EC2NetworkInterface](https://docs.aws.amazon.com/powershell/latest/reference/items/New-EC2NetworkInterface.html) cmdlet and set `Ipv4PrefixCount` to the number of IPv4 prefixes for AWS to assign. In the following example, AWS assigns one IPv4 prefix.
```
New-EC2NetworkInterface `
-SubnetId 'subnet-047cfed18eEXAMPLE' `
-Description 'IPv4 automatic example' `
-Ipv4PrefixCount 1
```
**To assign specific IPv4 prefixes during network interface creation**
Use the [New-EC2NetworkInterface](https://docs.aws.amazon.com/powershell/latest/reference/items/New-EC2NetworkInterface.html) cmdlet and set `Ipv4Prefix` to the prefixes. AWS selects IPv4 addresses from this range. In the following example, the prefix CIDR is 10.0.0.208/28.
```
Import-Module AWS.Tools.EC2
New-EC2NetworkInterface `
-SubnetId 'subnet-047cfed18eEXAMPLE' `
-Description 'IPv4 manual example' `
-Ipv4Prefix (New-Object `
-TypeName Amazon.EC2.Model.Ipv4PrefixSpecificationRequest `
-Property @{Ipv4Prefix = '10.0.0.208/28'})
```
**To assign automatic IPv6 prefixes during network interface creation**
Use the [New-EC2NetworkInterface](https://docs.aws.amazon.com/powershell/latest/reference/items/New-EC2NetworkInterface.html) cmdlet and set `Ipv6PrefixCount` to the number of IPv6 prefixes for AWS to assign. In the following example, AWS assigns one IPv6 prefix.
```
New-EC2NetworkInterface `
-SubnetId 'subnet-047cfed18eEXAMPLE' `
-Description 'IPv6 automatic example' `
-Ipv6PrefixCount 1
```
**To assign specific IPv6 prefixes during network interface creation**
Use the [New-EC2NetworkInterface](https://docs.aws.amazon.com/powershell/latest/reference/items/New-EC2NetworkInterface.html) cmdlet and set `Ipv6Prefixes` to the prefixes. AWS selects IPv6 addresses from this range. In the following example, the prefix CIDR is 2600:1f13:fc2:a700:1768::/80.
```
Import-Module AWS.Tools.EC2
New-EC2NetworkInterface `
-SubnetId 'subnet-047cfed18eEXAMPLE' `
-Description 'IPv6 manual example' `
-Ipv6Prefix (New-Object `
-TypeName Amazon.EC2.Model.Ipv6PrefixSpecificationRequest `
-Property @{Ipv6Prefix = '2600:1f13:fc2:a700:1768::/80'})
```
------
## Assign prefixes to an existing network interface
You can assign automatic or custom prefixes to an existing network interface.
------
#### [ Console ]
**To assign automatic prefixes to an existing network interface**
1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).
1. In the navigation pane, choose **Network Interfaces**.
1. Select the network interface to which to assign the prefixes, and choose **Actions**, **Manage prefixes**.
1. For **IPv4 prefix delegation** do one of the following:
+ To automatically assign an IPv4 prefix, choose **Auto-assign**. For **Number of IPv4 prefixes**, enter the number of prefixes to assign.
+ To assign a specific IPv4 prefix, choose **Custom**. Choose **Add new prefix** and enter the prefix.
1. For **IPv6 prefix delegation** do one of the following:
+ To automatically assign an IPv6 prefix, choose **Auto-assign**. For **Number of IPv6 prefixes**, enter the number of prefixes to assign.
+ To assign a specific IPv6 prefix, choose **Custom**. Choose **Add new prefix** and enter the prefix.
**Note**
**IPv6 prefix delegation** appears only if the selected subnet is enabled for IPv6.
1. Choose **Save**.
------
#### [ AWS CLI ]
Use the [assign-ipv6-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/assign-ipv6-addresses.html) command to assign IPv6 prefixes and the [assign-private-ip-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/assign-private-ip-addresses.html) command to assign IPv4 prefixes to existing network interfaces.
**To assign automatic IPv4 prefixes to an existing network interface**
Use the [assign-private-ip-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/assign-private-ip-addresses.html) command and set `--ipv4-prefix-count` to the number of IPv4 prefixes for AWS to assign. In the following example, AWS assigns one IPv4 prefix.
```
aws ec2 assign-private-ip-addresses \
--network-interface-id eni-081fbb4095EXAMPLE \
--ipv4-prefix-count 1
```
**To assign specific IPv4 prefixes to an existing network interface**
Use the [assign-private-ip-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/assign-private-ip-addresses.html) command and set `--ipv4-prefixes` to the prefix. AWS selects IPv4 addresses from this range. In the following example, the prefix CIDR is 10.0.0.208/28.
```
aws ec2 assign-private-ip-addresses \
--network-interface-id eni-081fbb4095EXAMPLE \
--ipv4-prefixes 10.0.0.208/28
```
**To assign automatic IPv6 prefixes to an existing network interface**
Use the [assign-ipv6-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/assign-ipv6-addresses.html) command and set `--ipv6-prefix-count` to the number of IPv6 prefixes for AWS to assign. In the following example, AWS assigns one IPv6 prefix.
```
aws ec2 assign-ipv6-addresses \
--network-interface-id eni-00d577338cEXAMPLE \
--ipv6-prefix-count 1
```
**To assign specific IPv6 prefixes to an existing network interface**
Use the [assign-ipv6-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/assign-ipv6-addresses.html) command and set `--ipv6-prefixes` to the prefix. AWS selects IPv6 addresses from this range. In the following example, the prefix CIDR is 2600:1f13:fc2:a700:18bb::/80.
```
aws ec2 assign-ipv6-addresses \
--network-interface-id eni-00d577338cEXAMPLE \
--ipv6-prefixes 2600:1f13:fc2:a700:18bb::/80
```
------
#### [ PowerShell ]
**To assign automatic IPv4 prefixes to an existing network interface**
Use the [Register-EC2PrivateIpAddress](https://docs.aws.amazon.com/powershell/latest/reference/items/Register-EC2PrivateIpAddress.html) cmdlet and set `Ipv4PrefixCount` to the number of IPv4 prefixes for AWS to assign. In the following example, AWS assigns one IPv4 prefix.
```
Register-EC2PrivateIpAddress `
-NetworkInterfaceId 'eni-00d577338cEXAMPLE' `
-Ipv4PrefixCount 1
```
**To assign specific IPv4 prefixes to an existing network interface**
Use the [Register-EC2PrivateIpAddress](https://docs.aws.amazon.com/powershell/latest/reference/items/Register-EC2PrivateIpAddress.html) cmdlet and set `Ipv4Prefix` to the prefix. AWS selects IPv4 addresses from this range. In the following example, the prefix CIDR is 10.0.0.208/28.
```
Register-EC2PrivateIpAddress `
-NetworkInterfaceId 'eni-00d577338cEXAMPLE' `
-Ipv4Prefix '10.0.0.208/28'
```
**To assign automatic IPv6 prefixes to an existing network interface**
Use the [Register-EC2Ipv6AddressList](https://docs.aws.amazon.com/powershell/latest/reference/items/Register-EC2Ipv6AddressList.html) cmdlet and set `Ipv6PrefixCount` to the number of IPv4 prefixes for AWS to assign. In the following example, AWS assigns one IPv6 prefix.
```
Register-EC2Ipv6AddressList `
-NetworkInterfaceId 'eni-00d577338cEXAMPLE' `
-Ipv6PrefixCount 1
```
**To assign specific IPv6 prefixes to an existing network interface**
Use the [Register-EC2Ipv6AddressList](https://docs.aws.amazon.com/powershell/latest/reference/items/Register-EC2Ipv6AddressList.html) cmdlet and set `Ipv6Prefix` to the prefix. AWS selects IPv6 addresses from this range. In the following example, the prefix CIDR is 2600:1f13:fc2:a700:18bb::/80.
```
Register-EC2Ipv6AddressList `
-NetworkInterfaceId 'eni-00d577338cEXAMPLE' `
-Ipv6Prefix '2600:1f13:fc2:a700:18bb::/80'
```
------
## Remove prefixes from your network interfaces
You can remove prefixes from an existing network interface.
------
#### [ Console ]
**To remove the prefixes from a network interface**
1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).
1. In the navigation pane, choose **Network Interfaces**.
1. Select the network interface.
1. Choose **Actions**, **Manage prefixes**.
1. For **IPv4 prefix delegation**, to remove specific prefixes, choose **Unassign** next to the prefixes to remove. To remove all prefixes, choose **Do not assign**.
1. For **IPv6 prefix delegation**, to remove specific prefixes, choose **Unassign** next to the prefixes to remove. To remove all prefixes, choose **Do not assign**.
**Note**
**IPv6 prefix delegation** appears only if the selected subnet is enabled for IPv6.
1. Choose **Save**.
------
#### [ AWS CLI ]
You can use the [unassign-ipv6-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/unassign-ipv6-addresses.html) command to remove IPv6 prefixes and the [unassign-private-ip-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/unassign-private-ip-addresses.html) commands to remove IPv4 prefixes from your existing network interfaces.
**To remove IPv4 prefixes from a network interface**
Use the [unassign-private-ip-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/unassign-private-ip-addresses.html) command and set `--ipv4-prefix` to the prefix CIDR to remove.
```
aws ec2 unassign-private-ip-addresses \
--network-interface-id eni-081fbb4095EXAMPLE \
--ipv4-prefixes 10.0.0.176/28
```
**To remove IPv6 prefixes from a network interface**
Use the [unassign-ipv6-addresses](https://docs.aws.amazon.com/cli/latest/reference/ec2/unassign-ipv6-addresses.html) command and set `--ipv6-prefix` to the prefix CIDR to remove.
```
aws ec2 unassign-ipv6-addresses \
--network-interface-id eni-00d577338cEXAMPLE \
--ipv6-prefix 2600:1f13:fc2:a700:18bb::/80
```
------
#### [ PowerShell ]
**To remove IPv4 prefixes from a network interface**
Use the [Unregister-EC2PrivateIpAddress](https://docs.aws.amazon.com/powershell/latest/reference/items/Unregister-EC2PrivateIpAddress.html) cmdlet and set `Ipv4Prefix` to the prefix CIDR to remove.
```
Unregister-EC2PrivateIpAddress `
-NetworkInterfaceId 'eni-00d577338cEXAMPLE' `
-Ipv4Prefix '10.0.0.208/28'
```
**To remove IPv6 prefixes from a network interface**
Use the [Unregister-EC2Ipv6AddressList](https://docs.aws.amazon.com/powershell/latest/reference/items/Unregister-EC2Ipv6AddressList.html) cmdlet and set `Ipv6Prefix` to the prefix CIDR to remove.
```
Unregister-EC2Ipv6AddressList `
-NetworkInterfaceId 'eni-00d577338cEXAMPLE' `
-Ipv6Prefix '2600:1f13:fc2:a700:18bb::/80'
```
------