Network interface attachments for your EC2 instance

You can create network interfaces to be used by your EC2 instances as primary or secondary network interfaces. You must attach a network interface to an EC2 instance if it is in the same Availability Zone as the network interface. The instance type of an instance determines how many network interfaces you can attach to the instance. For more information, see Maximum IP addresses per network interface.

Considerations

• You can attach a network interface to an instance when it's running (hot attach), when it's stopped (warm attach), or when the instance is being launched (cold attach).

• You can detach secondary network interfaces when the instance is running or stopped. However, you can't detach the primary network interface.

• You can detach a secondary network interface from one instance and attach it to another instance.

• When launching an instance using the CLI, API, or an SDK, you can specify the primary network interface and additional network interfaces.

• Launching an Amazon Linux or Windows Server instance with multiple network interfaces automatically configures interfaces, private IPv4 addresses, and route tables on the operating system of the instance.

• A warm or hot attach of an additional network interface might require you to manually bring up the second interface, configure the private IPv4 address, and modify the route table accordingly. Instances running Amazon Linux or Windows Server automatically recognize the warm or hot attach and configure themselves.

• You can't attach another network interface to an instance (for example, a NIC teaming configuration) to increase or double the network bandwidth to or from the dual-homed instance.

• If you attach multiple network interfaces from the same subnet to an instance, you might encounter networking issues such as asymmetric routing. If possible, add a secondary private IPv4 address on the primary network interface instead.

• For EC2 instances in an IPv6-only subnet, if you attach a secondary network interface, the private DNS hostname of the secondary network interface resolves to the primary IPv6 address for the primary network interface.

• [Windows instances] – If you add multiple network interfaces to an instance, you must configure the network interfaces to use static routing.

Attach a network interface

You can attach a network interface to any instance in the same Availability Zone as the network interface, using either the Instances or Network Interfaces page of the Amazon EC2 console. Alternatively, you can specify existing network interfaces when you launch instances.

If the public IPv4 address on your instance is released, it does not receive a new one if there is more than one network interface attached to the instance. For more information about the behavior of public IPv4 addresses, see Public IPv4 addresses.

Instances page

To attach a network interface to an instance using the Instances page

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

2. In the navigation pane, choose Instances.

3. Select the checkbox for the instance.

4. Choose Actions, Networking, Attach network interface.

5. Choose a VPC. The network interface can reside in the same VPC as your instance or in a different VPC that you own, as long as the network interface is in the same Availability Zone as the instance. This enables you to create multi-homed instances across VPCs with different networking and security configurations.

6. Select a network interface. If the instance supports multiple network cards, you can choose a network card.

7. Choose Attach.

Network Interfaces page

To attach a network interface to an instance using the Network Interfaces page

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

2. In the navigation pane, choose Network Interfaces.

3. Select the checkbox for the network interface.

4. Choose Actions, Attach.

5. Choose an instance. If the instance supports multiple network cards, you can choose a network card.

6. Choose Attach.

To attach a network interface to an instance using the command line

You can use one of the following commands. For more information about these command line interfaces, see Access Amazon EC2.

• attach-network-interface (AWS CLI)

• Add-EC2NetworkInterface (AWS Tools for Windows PowerShell)

Detach a network interface

You can detach a secondary network interface that is attached to an EC2 instance at any time, using either the Instances or Network Interfaces page of the Amazon EC2 console.

If you try to detach a network interface that is attached to a resource from another service, such as an Elastic Load Balancing load balancer, a Lambda function, a WorkSpace, or a NAT gateway, you get an error that you do not have permission to access the resource. To find which service created the resource attached to a network interface, check the description of the network interface. If you delete the resource, then its network interface is deleted.

Instances page

To detach a network interface from an instance using the Instances page

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

2. In the navigation pane, choose Instances.

3. Select the checkbox for the instance. Check the Network interfaces section of the Networking tab to verify that the network interface is attached to an instance as a secondary network interface.

4. Choose Actions, Networking, Detach network interface.

5. Select the network interface and choose Detach.

Network Interfaces page

To detach a network interface from an instance using the Network Interfaces page

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

2. In the navigation pane, choose Network Interfaces.

3. Select the checkbox for the network interface. Check the Instance details section of the Details tab to verify that the network interface is attached to an instance as a secondary network interface.

4. Choose Actions, Detach.

5. When prompted for confirmation, choose Detach.

6. If the network interface fails to detach from the instance, choose Force detachment, Enable and then try again. We recommend that force detachment only as a last resort. Forcing a detachment can prevent you from attaching a different network interface on the same index until you restart the instance. It can also prevent the instance metadata from reflecting that the network interface was detached until you restart the instance.

To detach a network interface using the command line

You can use one of the following commands. For more information about these command line interfaces, see Access Amazon EC2.

• detach-network-interface (AWS CLI)

• Dismount-EC2NetworkInterface (AWS Tools for Windows PowerShell)