Every instance in a VPC has a default network interface, called the primary network interface (eth0). You cannot detach a primary network interface from an instance. You can create and attach additional network interfaces (admin, VoIP, data, local).

1. Access the EC2 Dashboard and click Network Interfaces under Network Security on the left panel.
2. Click Create Network Interfaces.
3. Specify the name of the interface and choose the Subnet and Security group to associate the Interface.
4. Return to the homepage of the EC2 Dashboard and click Running Instances.
5. Select your first instance and ensure it is highlighted.
6. Open the Actions drop-down and select Networking, Attach Network Interface.
7. From the Attach Network Interface pop-up, select your first network interface name.
8. Repeat these steps for all network interfaces and all of your instances you have created.