# Design considerations

This section contains design advice that you might want to keep in mind when using AWS in Parallels RAS.

## **DHCP options set**

You might need to use an AWS DHCP options set to specify a custom DNS pointing to the domain controller so that the VMs created from templates are able to join the Active Directory domain. If the custom DNS is not set, the default AWS public DNS will be used, and the VMs won't be able to communicate with the domain controller. 

For information on how to configure DHCP options sets, see <https://docs.aws.amazon.com/vpc/latest/userguide/DHCPOptionSet.html>.

The Provider Agent and Guest Agents need to be on the same subnet for the Guest Agent to discover the Provider Agent using broadcasts. If this is not possible, then a registry setting with the IP of the Provider Agent needs to be added on the VM as described here: <https://kb.parallels.com/en/124157?language=en>.

## **Service quotas**

Sometimes solutions scale in usage, invocations, number of instances, and so on. Due to this, the standard AWS service quotas can be reached. For more information about AWS service quotas, see <https://docs.aws.amazon.com/general/latest/gr/aws_service_limits.html>.

Parallels RAS integrations are subject to the EC2 and EBS endpoint limits as specified here:

* <https://docs.aws.amazon.com/general/latest/gr/ec2-service.html>
* <https://docs.aws.amazon.com/general/latest/gr/ebs-service.html>

## **Encrypting storage**

The storage of clones created from RAS templates will be encrypted if the AWS administrator enables encryption of the RAS template VM storage in AWS Management Console.

Encryption can be enabled by default or explicitly when launching a new EC2 VM:

<figure><img src="/files/0MQJDuLmfqnrQzNNi7DZ" alt="Encrypting storage"><figcaption></figcaption></figure>

For more information about encryption, see <https://aws.amazon.com/blogs/compute/must-know-best-practices-for-amazon-ebs-encryption/>.


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