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Step

Details

Create a new interface.

Click on Create Network Interface at the top of the interface list.

This opens the interface creation window.

On this screen,

enter a description,
select the subnet the interface should be on (select the subnet to which your instance is to be connected),
allow AWS to automatically assign a private IP address or set a custom one from the subnet IP range, and
associate the interface with a security group (often the same as for the instance).

Click on Create when you are done. The new interface will appear in the overview list. There you can assign a name to the interface. Check that the interface is in state available.

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Stopping and restarting the instance after adding a second network interface will release any automatically assigned public IP address. If several interfaces are required where one or more are configured with a public address, use Elastic IP addresses.
Additionally, adding a second network interface with an IP configuration to a non-Amazon Linux EC2 instance causes traffic flow issues. This occurs in cases of asymmetric routing where traffic to the instance arrives at one network interface and leaves the instance through the other network interface. This is blocked by AWS because of a mismatch between MAC address and IP address. Refer to the AWS documentation and the Charon -SSP Cloud Networking Information chapter (section asymmetric routing considerations Asymmetric Routing Considerations) for more information. Failure to use the proper steps, may make your instance unreachable!
If your instance supports enhanced networking there may be naming inconsistencies when adding additional interfaces to a running instance. Please refer to the interface naming section below and the AWS documentation.
The Charon-SSP specific: the NetworkManager is disabled on Charon-SSP AWS marketplace images that are based on Linux 7.x. Therefore, instances based on such images require manually created ifcfg-files in /etc/sysconfig/network-scripts to define the IP configuration for additional interfaces before the Charon Manager can be used to manage it.

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Step	Details
Locate the Elastic IPs option on the EC2 dashboard and click on it.	This will list the already created Elastic IP addresses.
Allocate a new Elastic IP address.	In the overview list, click on Allocate Elastic IP address if you need to allocate a new address. It is also possible to assign an existing address to an interface. However, each address can only be used for one instance. This will open the address allocation window.
	In the address allocation window, select the Amazon pool (or your own pool of public addresses), and click on Allocate. The new address will be shown in the list.
Associate the address with the network interface.	Select the address. Then select Actions > Associate Elastic IP address. A window to enter the required options opens. In the window, select to associate the IP address with a network interface, select your network interface from the drop-down menu, connect the public address to the private address of the interface, and click on Associate to complete the step.