An Azure DNS forwarder, in the context of hybrid networking, refers to a setup where a conditional forwarder on your on-premises DNS server directs DNS requests to Azure. This is often used in scenarios where you have resources both on-premises and in Azure, allowing for seamless name resolution across both environments.
How it Works
Here’s a breakdown of how an Azure DNS forwarder typically operates:
- On-Premises Request: When a device on your on-premises network needs to resolve a domain name that might be hosted in Azure, the on-premises DNS server initially handles the request.
- Conditional Forwarding: Instead of resolving the name directly, the on-premises DNS server is configured with a conditional forwarder. This means it is set up to forward queries for a specific domain (e.g., the domain name of your private Azure DNS zone) to a specific Azure DNS server or resolver.
- Azure Resolution: The request is then sent to Azure DNS, which handles the resolution. If the domain is a private DNS zone that is linked to an Azure virtual network, Azure DNS will look up the appropriate private IP address.
- Response: Azure DNS sends the resolved IP address back to the on-premises DNS server, which then forwards it to the original requesting device.
Key Components
| Component | Description |
|---|---|
| On-Premises DNS Server | Your existing DNS server in your local network, configured with a conditional forwarder. |
| Conditional Forwarder | A specific configuration on your on-premises DNS server that directs DNS requests to Azure based on the domain being queried. |
| Azure DNS | Azure's DNS service that hosts your private DNS zones and resolves requests forwarded from on-premises. |
| Private DNS Zone | A private DNS zone hosted in Azure, linked to a virtual network, containing records for your Azure resources (allowing resolution of internal azure resources). |
| Virtual Network | The Azure network that your resources reside in and your private DNS zone is linked to. |
Practical Use Cases
- Hybrid Environments: Allows name resolution for resources residing both on-premises and within Azure virtual networks, enabling a seamless hybrid environment.
- Consistent Naming: Maintain a consistent naming scheme for resources across on-premises and Azure.
- Simplified Management: Reduces the need to manually manage DNS records across different environments by leveraging a single DNS system.
Example
Let’s say you have a service running in Azure with a private IP and a private DNS record such as service.private.contoso.com.
- A computer on your on-premises network tries to reach the service using that name (
service.private.contoso.com). - Your on-premises DNS server is configured to forward all requests for the
private.contoso.comdomain to your Azure DNS. - Azure DNS resolves
service.private.contoso.comto its corresponding private IP address and sends this back. - The on-premises computer receives this IP and is now able to reach the Azure service.
By using a conditional forwarder on your on-premises DNS, you integrate your on-premise DNS with your Azure DNS ensuring name resolution for resources both on premises and in azure.
