Consistent DNS resolution in a hybrid hub spoke network topology
DNS is one of the most essential networking services, next to IP routing. A modern hybrid cloud network may have various sources of DNS: Azure Private DNS Zones, public DNS, domain controllers, etc. Some organizations may also prefer to route their public Internet DNS queries through a specific DNS provider. Therefore, it is crucial to ensure consistent DNS resolution across the whole (hybrid) network. This article describes how DNS Private Resolver can be leveraged to build such architecture.Lesson Learned #110 Azure SQL Managed Instance and Azure DNS
I got this recent case where customer wanted to create a transaction replication from Azure SQL Managed instance to another SQL Server inside the same virtual network, but in a different subnet, but all inside Azure. All communications that happens on Azure Network if not set a custom DNS will use Azure DNS to resolve name of resources inside the network. However there is something very important in the documentation https://docs.microsoft.com/en-us/azure/virtual-network/virtual-networks-name-resolution-for-vms-and-role-instances#azure-provided-name-resolution "Azure-provided name resolution Along with resolution of public DNS names, Azure provides internal name resolution for VMs and role instances that reside within the same virtual network or cloud service. VMs and instances in a cloud service share the same DNS suffix, so the host name alone is sufficient. But in virtual networks deployed using the classic deployment model, different cloud services have different DNS suffixes. In this situation, you need the FQDN to resolve names between different cloud services. In virtual networks deployed using the Azure Resource Manager deployment model, the DNS suffix is consistent across the virtual network, so the FQDN is not needed. DNS names can be assigned to both VMs and network interfaces. Although Azure-provided name resolution does not require any configuration, it is not the appropriate choice for all deployment scenarios, as detailed in the previous table." Consider a Azure Resource Manager deployment it would not be necessary to use FQDN, however the way that the deployment of Azure SQL Managed Instance happens it will not share the same DNS sufix and we can see connectivity errors There are some workarounds: use the private IP or the FQDN of the SQL VM. The default DNS sufix is documented in same article above ( https://docs.microsoft.com/en-us/azure/virtual-network/virtual-networks-name-resolution-for-vms-and-role-instances#name-resolution-that-uses-your-own-dns-server ) "When you are using Azure-provided name resolution, Azure Dynamic Host Configuration Protocol (DHCP) provides an internal DNS suffix (.internal.cloudapp.net) to each VM. This suffix enables host name resolution because the host name records are in the internal.cloudapp.net zone. When you are using your own name resolution solution, this suffix is not supplied to VMs because it interferes with other DNS architectures (like domain-joined scenarios). Instead, Azure provides a non-functioning placeholder (reddog.microsoft.com)." For this test I will create a linked server from SQL MI to SQL VM and we can see that I was able to connect with success to IP and VM.internal.cloudapp.net, but failing to simple VM name This behavior is also documented at https://docs.microsoft.com/en-us/azure/sql-database/sql-database-managed-instance-custom-dns "An Azure SQL Database Managed Instance must be deployed within an Azure virtual network (VNet). There are a few scenarios (for example, db mail, linked servers to other SQL instances in your cloud or hybrid environment) that require private host names to be resolved from the Managed Instance. In this case, you need to configure a custom DNS inside Azure. Since Managed Instance uses the same DNS for its inner workings, you need to configure the custom DNS server so that it can resolve public domain names. Important Always use fully-qualified domain names (FQDN) for the mail servers, SQL Servers, and other services even if they are within your private DNS zone. For example use smtp.contoso.com for mail server because simple smtp will not be properly resolved."
AZ-700 Step by Step Guide for Azure Private DNS
This article is part of our AZ-700 series, offering a step-by-step guide on configuring Azure Private DNS, based on the tutorial available on YouTube. I highly recommend watching the video to gain a solid understanding of the concepts covered in this article. Through this guide, you'll gain hands-on experience in setting up and managing Azure Private DNS, enabling efficient DNS resolution, network segmentation, and seamless automation within Microsoft Azure. In today’s cloud environment, managing network resources and ensuring secure connectivity across virtual networks (vNets) can be complex, particularly when DNS management comes into play. This article provides a comprehensive, hands-on guide to setting up and configuring Azure Private DNS for efficient DNS resolution, network segmentation, and seamless automation in Microsoft Azure. Follow along as we explore the essential elements, from linking vNets and subnets to DNS automation. Why Azure Private DNS? Azure Private DNS allows you to manage and resolve DNS names within a virtual network without exposing them to the public internet. It simplifies domain name resolution, enhances security, and enables automation for dynamic environments. Key benefits of using Azure Private DNS: Dynamic DNS Management: Automatically updates DNS records for new or deleted resources, eliminating stale or "dangling" DNS entries. Domain Delegation: Allows centralized DNS management by delegating your corporate domain to Azure Private DNS. Enhanced Security: DNS records are automatically removed when resources are deleted, ensuring up-to-date and secure network configuration. Quick Recap: Azure Networking Fundamentals Before diving into Azure Private DNS, let’s revisit some foundational concepts from our previous discussions: vNet (Virtual Network): Similar to a traditional VLAN but without broadcast support, a vNet enables secure and scalable resource management. Subnet: Subdivision within a vNet, allowing more granular control over resource segmentation. Azure allows you to set up a single vNet with multiple subnets, maximizing network organization and security without the broadcast overhead typical in traditional networks. Step 1: Understanding Azure Private DNS Azure Private DNS enables the automatic registration of DNS names for resources within your vNet. For example, when you create a virtual machine (VM) in a vNet linked to a private DNS zone, the VM’s name and IP address automatically register within the zone. This streamlines DNS management, especially for dynamic environments where resources are created and deleted frequently. Key Features Automatic DNS Registration: Automatically updates the DNS zone with new or removed resources. Domain Delegation: You can delegate your corporate domain to the private DNS zone, managing DNS records centrally within Azure. Support for All DNS Record Types: Azure DNS supports a full range of DNS records, including A, AAAA, CNAME, and MX records. Step 2: Setting Up the Private DNS Zone 1. Create a Private DNS Zone In the Azure Portal, navigate to Private DNS Zones and create a new zone. Define a name for the DNS zone, such as yourdomain.private. Deploy the DNS zone and navigate to the resource. 2. Link vNets for Automatic DNS Registration Within the Private DNS Zone resource, select Virtual Network Links to connect vNets to the DNS zone. For each vNet (e.g., Core Services, West Europe, Asia), specify the vNet link and enable Auto Registration. This enables seamless DNS name resolution across linked vNets and allows automatic DNS record updates when resources are created or deleted. Step 3: Verifying DNS Resolution and Connectivity Verify DNS Records in the Private DNS Zone: Go to DNS Management under the Private DNS zone and check that the A records for the VMs appear. Connect to VMs via DNS: Use Remote Desktop to access one VM, then attempt to connect to the other VM by its DNS name (rather than IP address). This confirms that the Private DNS setup allows for name-based connectivity. If issues arise (e.g., timeouts), ensure that firewall settings permit connectivity between the VMs. Step 4: DNS Zone Peering Across Regions With Azure Private DNS, you can link vNets across different regions, allowing resources in different geographic locations to resolve names and connect seamlessly. Link vNets Across Regions: Connect the vNets in regions like West Europe, East US, and Asia to the Private DNS zone. Verify Regional Connectivity: From a VM in one region (e.g., Asia), test connectivity to a VM in another region (e.g., East US) using DNS names. Azure Private DNS allows DNS name resolution across regions, ensuring consistent and reliable network connectivity. Summary Setting up Azure Private DNS is a powerful way to automate and centralize DNS management within a virtual network environment. This guide provides a practical framework for deploying Private DNS zones, linking vNets, and verifying connectivity. By configuring Azure Private DNS, organizations can streamline DNS management, secure network configurations, and enhance connectivity across geographically dispersed resources. Next Steps In future tutorials, we’ll explore VNet peering for advanced network configurations, allowing secure communication between isolated virtual networks. Be sure to subscribe and stay tuned for more Azure networking tips and tricks! Let’s enhance your Azure network management with practical, hands-on solutions.Faking DDNS with Azure Services
I want to access my “on-prem lab” environment from anywhere but my ISP cycles my IP address regularly. I could always use a service like noip.com or dyndns but I already have a DNS zone managed in Azure DNS and I thought it would be fun to figure out how to use it for my needs. You can leverage multiple Azure services and configuration to address on-prem issues efficiently.
