# AWS ParallelCluster using two subnets
<a name="network-configuration-v3-two-subnets"></a>

In this configuration, only the head node of the cluster is required to have a public IP assigned. You can achieve this 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).

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 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*.

This configuration requires a [NAT gateway](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html) or an internal proxy in the subnet used for the queues, to give internet access to the compute instances.

 ![\[ParallelCluster using two subnets\]](http://docs.aws.amazon.com/parallelcluster/latest/ug/images/two-subnets.png) 

 The configuration to use an existing private subnet for compute instances 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-23456789 # subnet with NAT gateway
        #AssignPublicIp: false
```