# AWS ParallelCluster in a single public subnet
<a name="network-configuration-v3-single-subnet"></a>

In this configuration, all instances of the cluster must be assigned a public IP in order to get internet access. To achieve this, do the following:
+ Make sure the head node is assigned a public IP address by either turning on the "Enable auto-assign public IPv4 address" setting for the subnet used in [`HeadNode`](HeadNode-v3.md) / [`Networking`](HeadNode-v3.md#HeadNode-v3-Networking) / [`SubnetId`](HeadNode-v3.md#yaml-HeadNode-Networking-SubnetId) or by assigning an Elastic IP in [`HeadNode`](HeadNode-v3.md) / [`Networking`](HeadNode-v3.md#HeadNode-v3-Networking) / [`ElasticIp`](HeadNode-v3.md#yaml-HeadNode-Networking-ElasticIp).
+ Make sure the compute nodes are assigned a public IP address by either turning on the "Enable auto-assign public IPv4 address" setting for the subnet used in [`Scheduling`](Scheduling-v3.md) / [`SlurmQueues`](Scheduling-v3.md#Scheduling-v3-SlurmQueues) / [`Networking`](Scheduling-v3.md#Scheduling-v3-SlurmQueues-Networking) / [`SubnetIds`](Scheduling-v3.md#yaml-Scheduling-SlurmQueues-Networking-SubnetIds) or by setting [`AssignPublicIp`](Scheduling-v3.md#yaml-Scheduling-SlurmQueues-Networking-AssignPublicIp): true in [`Scheduling`](Scheduling-v3.md) / [`SlurmQueues`](Scheduling-v3.md#Scheduling-v3-SlurmQueues) / [`Networking`](Scheduling-v3.md#Scheduling-v3-SlurmQueues-Networking).
+ If you define a p4d instance type, or another instance type that has multiple network interfaces or a network interface card to the head node, you must set [`HeadNode`](HeadNode-v3.md) / [`Networking`](HeadNode-v3.md#HeadNode-v3-Networking) / [`ElasticIp`](HeadNode-v3.md#yaml-HeadNode-Networking-ElasticIp) to `true` to provide public access. AWS public IPs can only be assigned to instances launched with a single network interface. For this case, we recommend that you use a [NAT gateway](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html) to provide public access to the cluster compute nodes. For more information on IP addresses, see [Assign a public IPv4 address during instance launch](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-instance-addressing.html#public-ip-addresses) in the *Amazon EC2 User Guide for Linux Instances*.
+ You can't define a p4d or hp6id instance type, or another instance type that has multiple network interfaces or a network interface card to compute nodes because AWS public IPs can only be assigned to instances launched with a single network interface. For more information on IP addresses, see [Assign a public IPv4 address during instance launch](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-instance-addressing.html#public-ip-addresses) in the *Amazon EC2 User Guide for Linux Instances*.
+ Starting with AWS ParallelCluster version 3.15.0, this requirement also applies when you enable [Efa](Scheduling-v3.md#yaml-Scheduling-SlurmQueues-ComputeResources-Efa) on a single-network-card instance type that supports more than one network interface. AWS ParallelCluster launches these compute nodes with multiple network interfaces, and AWS public IPs can only be assigned to instances launched with a single network interface. Use a private subnet with a [NAT gateway](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html) for these compute nodes instead, as described in [AWS ParallelCluster using two subnets](network-configuration-v3-two-subnets.md).

For more information, see [ Enabling internet access](https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Internet_Gateway.html#vpc-igw-internet-access) in *Amazon VPC User Guide*.

 ![ParallelCluster in a single public subnet](http://docs.aws.amazon.com/parallelcluster/latest/ug/images/single-public-subnet.png) 

 The configuration for this architecture requires the following settings:

```
# Note that all values are only provided as examples
HeadNode:
  ...
  Networking:
    SubnetId: subnet-12345678 # subnet with internet gateway
    #ElasticIp: true | false | eip-12345678
Scheduling:
  Scheduler: slurm
  SlurmQueues:
    - ...
      Networking:
        SubnetIds:
          - subnet-12345678 # subnet with internet gateway
        #AssignPublicIp: true
```