# Multiple network interfaces in AWS PCS
<a name="working-with_networking_multi-nic"></a>

Some EC2 instances have multiple network cards. This allows them to provide higher network performance, including bandwidth capabilities above 100 Gbps and improved packet handling. For more information about instances with multiple network cards, see [Elastic network interfaces](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html#network-cards) in the *Amazon Elastic Compute Cloud User Guide*.

 Configure additional network cards for instances in an AWS PCS compute node group by adding network interfaces to its EC2 launch template. Below is an example launch template that enables two network cards, such as can be found on an `hpc7a.96xlarge` instance. Note the following details: 
+ The subnet for each network interface must be the same as you choose when configuring the AWS PCS compute node group that will use the launch template.
+ The primary network device, where routine network communication such as SSH and HTTPS traffic will occur, is established by setting a `DeviceIndex` of `0`. Other network interfaces have a `DeviceIndex` of `1`. There can only be one primary network interface—all other interfaces are secondary.
+ All network interfaces must have a unique `NetworkCardIndex`. A recommended practice is to number them sequentially as they are defined in the launch template.
+ Security groups for each network interface are set using `Groups`. In this example, an inbound SSH security group (`sg-SshSecurityGroupId`) is added to the primary network interface, as well as the security group enabling within-cluster communications (`sg-ClusterSecurityGroupId`). Finally, a security group allowing outbound connections to the internet (`sg-InternetOutboundSecurityGroupId`) is added to both primary and secondary interfaces.

```
{
    "NetworkInterfaces": [
        {
            "DeviceIndex": 0,
            "NetworkCardIndex": 0,
            "SubnetId": "subnet-SubnetId",
            "Groups": [
               "sg-SshSecurityGroupId",
               "sg-ClusterSecurityGroupId",
               "sg-InternetOutboundSecurityGroupId"
            ]
        },
        {
            "DeviceIndex": 1,
            "NetworkCardIndex": 1,
            "SubnetId": "subnet-SubnetId",
            "Groups": ["sg-InternetOutboundSecurityGroupId"]
        }
    ]
}
```