How to Troubleshoot DNS Issues on an Azure Virtual Machine
Question details
The user needs to resolve a DNS-related issue causing a custom domain mapped to an Azure Virtual Machine to display a blank page.
- Product
- Azure Virtual Machine
- Device & OS
- not provided
- Scenario
- Accessing a custom domain mapped to an Azure-hosted virtual machine via a vendor application.
- Observed behavior
- The domain displays a blank page when opened, and the vendor suspects a DNS configuration issue despite settings appearing correct.
Ensure you have access to your DNS hosting provider's management console and administrator credentials for the Azure Virtual Machine to run command-line diagnostics.
Verify DNS Records and Propagation with Hosting Provider
Check your DNS hosting provider's dashboard to ensure the required A and CNAME records are correctly configured and have fully propagated.
Incorrect DNS records or incomplete DNS propagation are the most common reasons a custom domain fails to load or displays a blank page when connected to an Azure Virtual Machine.
Access the management console of your domain registrar or DNS hosting provider.
Navigate to the DNS management section. Verify that your A record points directly to the public IP address of your Azure VM, and ensure any required CNAME records are accurately mapped.
Use an online DNS checker tool to verify globally that the DNS records have successfully propagated to the correct Azure IP address.
Test DNS Resolution from the Azure Virtual Machine
Run local diagnostic commands directly on the Azure Virtual Machine to determine if the server can successfully resolve the custom domain.
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Frequently Asked Questions
Why is my custom domain showing a blank page on Azure?
A blank page often indicates that the web server is not receiving the request correctly. This can be caused by missing or incorrect A or CNAME DNS records pointing to the Virtual Machine, or the vendor application not being correctly bound to the domain.
How long does it take for DNS changes to propagate to my Azure VM?
DNS propagation typically takes between a few minutes to 48 hours. The exact time depends on the TTL (Time to Live) settings configured at your DNS hosting provider before the changes were made.
What should I do if nslookup fails on my Azure Virtual Machine?
If nslookup fails, check the virtual network (VNet) DNS server settings in the Azure portal. Ensure the VM is using the correct Azure-provided DNS or your own custom DNS servers, and verify that there are no Network Security Group (NSG) rules blocking port 53.
