How to Resolve On-Premises Domains from AWS and Vice Versa

In today’s hybrid cloud environments, seamless integration between on-premises infrastructure and cloud services is critical. One of the key challenges in such setups is ensuring that DNS resolution works flawlessly across both environments. AWS provides a powerful solution for this challenge through Route 53 Resolver and AD Connector. This article will guide you through building a hybrid DNS architecture that allows you to resolve on-premises domains from AWS and vice versa. We’ll cover the technical details, code snippets, use cases, real-life implementations, and step-by-step instructions for both CLI-based and AWS Console-based setups.

Introduction to Hybrid DNS Architecture

In a hybrid cloud setup, organizations often have resources hosted both on-premises and in the cloud. For example, you might have an on-premises Active Directory (AD) domain and applications running in AWS. To ensure smooth communication between these environments, DNS resolution must work bidirectionally:

1. On-premises to AWS: Resolve AWS-hosted domains (e.g., example.aws) from on-premises systems.
2. AWS to On-premises: Resolve on-premises domains (e.g., example.local) from AWS resources.

AWS Route 53 Resolver acts as a bridge between on-premises DNS and AWS DNS, enabling seamless resolution across both environments. AD Connector simplifies the integration of AWS resources with on-premises Active Directory.

Key Components of the Architecture

1. Route 53 Resolver: A service that enables DNS resolution between your VPCs and your on-premises network.
2. AD Connector: A proxy service that connects AWS resources to your on-premises Active Directory without requiring synchronization.
3. On-premises DNS Server: Typically a Windows Server running DNS services for your on-premises domain.
4. AWS VPC: The virtual network where your AWS resources reside.
5. Security Groups and NACLs: To control traffic flow between on-premises and AWS.

Use Cases

1. Hybrid Applications: Applications that span on-premises and AWS environments require DNS resolution for both.
2. Active Directory Integration: AWS resources need to authenticate against on-premises AD.
3. Disaster Recovery: Failover between on-premises and AWS resources requires seamless DNS resolution.
4. Centralized DNS Management: Manage DNS records for both environments from a single pane.

Prerequisites

Before diving into the implementation, ensure the following:

1. An on-premises Active Directory with DNS services configured.
2. An AWS account with sufficient permissions to create VPCs, Route 53 Resolver endpoints, and AD Connector.
3. A VPC in AWS with at least two subnets in different Availability Zones.
4. VPN or Direct Connect configured between your on-premises network and AWS VPC.

Step-by-Step Implementation

Step 1: Set Up Route 53 Resolver Endpoints

Route 53 Resolver endpoints allow DNS queries to flow between your VPC and on-premises network.

AWS Console Steps:

1. Open the Route 53 Console.
2. In the left navigation pane, choose Resolver.
3. Click Create endpoint.
4. Provide a name for the endpoint (e.g., OnPremisesResolver).
5. Select the VPC where you want to create the endpoint.
6. Choose the subnets and security groups for the endpoint.
7. Specify the IP addresses for the inbound and outbound endpoints.
8. Click Create.

CLI Steps:

aws route53resolver create-resolver-endpoint \
    --name OnPremisesResolver \
    --direction INBOUND \
    --security-group-ids sg-0123456789abcdef0 \
    --ip-addresses SubnetId=subnet-0123456789abcdef0,Ip=10.0.1.10 SubnetId=subnet-0123456789abcdef1,Ip=10.0.2.10 \
    --creator-request-id unique-string \
    --region us-east-1

Step 2: Configure DNS Forwarding Rules

DNS forwarding rules allow Route 53 Resolver to forward DNS queries for specific domains to your on-premises DNS server.

AWS Console Steps:

1. Open the Route 53 Console.
2. In the left navigation pane, choose Resolver.
3. Click Create rule.
4. Provide a name for the rule (e.g., OnPremisesForwardingRule).
5. Specify the domain name (e.g., example.local).
6. Add the IP addresses of your on-premises DNS servers.
7. Associate the rule with the VPC.
8. Click Create.

CLI Steps:

aws route53resolver create-resolver-rule \
    --name OnPremisesForwardingRule \
    --rule-type FORWARD \
    --domain-name example.local \
    --target-ips Ip=192.168.1.10 \
    --resolver-endpoint-id rslvr-0123456789abcdef0 \
    --region us-east-1

Step 3: Set Up AD Connector

AD Connector allows AWS resources to authenticate against your on-premises Active Directory.

AWS Console Steps:

1. Open the Directory Service Console.
2. Click Set up directory.
3. Choose AD Connector.
4. Provide the DNS name of your on-premises domain (e.g., example.local).
5. Specify the IP addresses of your on-premises DNS servers.
6. Provide the service account credentials for your AD.
7. Choose the VPC and subnets for the AD Connector.
8. Click Create.

CLI Steps:

aws ds create-directory \
    --name example.local \
    --password YourADPassword \
    --size Small \
    --vpc-settings VpcId=vpc-0123456789abcdef0,SubnetIds=subnet-0123456789abcdef0,subnet-0123456789abcdef1 \
    --type ADConnector \
    --region us-east-1

Step 4: Test DNS Resolution

Once the setup is complete, test DNS resolution in both directions.

From AWS to On-Premises:

1. Launch an EC2 instance in the VPC.
2. SSH into the instance.
3. Run the following command to resolve an on-premises domain:

nslookup example.local

From On-Premises to AWS:

1. On an on-premises machine, run the following command to resolve an AWS-hosted domain:

nslookup example.aws

Step 5: Monitor and Troubleshoot

Use CloudWatch Logs and Metrics to monitor DNS resolution and troubleshoot issues.

Enable Query Logging:

1. Open the Route 53 Console.
2. In the left navigation pane, choose Resolver.
3. Click Query logging.
4. Click Configure query logging.
5. Select the VPC and CloudWatch Logs group.
6. Click Create.

CLI Steps:

aws route53resolver create-resolver-query-log-config \
    --name QueryLogConfig \
    --destination-arn arn:aws:logs:us-east-1:123456789012:log-group:/aws/route53/resolver \
    --region us-east-1

Real-Life Implementation: Case Study

A financial services company with an on-premises Active Directory and AWS-hosted applications needed seamless DNS resolution for their hybrid environment. By implementing Route 53 Resolver and AD Connector, they achieved:

1. Bidirectional DNS Resolution: Applications in AWS could resolve on-premises domains and vice versa.
2. Centralized Management: DNS records were managed centrally, reducing administrative overhead.
3. Improved Security: DNS queries were encrypted over VPN, ensuring data security.

Best Practices

1. Use Private Hosted Zones: For AWS-hosted domains, use Route 53 private hosted zones.
2. Enable Query Logging: Monitor DNS queries for troubleshooting and auditing.
3. Secure Communication: Use VPN or Direct Connect for secure communication between on-premises and AWS.
4. Regularly Update DNS Records: Ensure DNS records are up-to-date to avoid resolution failures.

Conclusion

Building a hybrid DNS architecture with Route 53 Resolver and AD Connector is a powerful way to enable seamless DNS resolution between on-premises and AWS environments. By following the steps outlined in this article, you can ensure that your hybrid cloud setup is robust, secure, and efficient. Whether you’re managing hybrid applications, integrating Active Directory, or planning for disaster recovery, this architecture provides a solid foundation for your DNS needs.