244 字
1 分鐘
Troubleshooting Web App DNS Resolution (Public / Private Switching)
2026-04-15
Conclusion
A single Azure Web App resolving to different IPs is determined by whether it uses Private Link DNS.
Applicable Scenarios
- Troubleshooting Azure Web App connectivity issues
- Validating Private Endpoint / Private Link configurations
- Determining if traffic is internal or external
- DevOps / Infra troubleshooting
Process Steps
1. Verify DNS Resolution Results Using nameresolver
- Run
nameresolver.exein Kudu or Web App console to query the domain - Observe whether it resolves to a public IP (13.x.x.x) or a private IP (10.x.x.x)
- This is the fastest way to confirm the “traffic path”
nameresolver.exe website.azurewebsites.net2. Determine Public vs Private DNS Behavior
- Resolves to public:
- domain → *.azurewebsites.net
- IP is 13.x.x.x
- Indicates traffic goes over Azure public network
- Resolves to private:
- domain → *.privatelink.azurewebsites.net
- IP is 10.x.x.x
- Indicates traffic goes over Private Endpoint The key difference lies in whether the DNS is “overridden by a Private DNS Zone”.
3. Confirm Private Link / DNS Zone Configuration
-
If a Private Endpoint is created:
- Azure will create
privatelinkDNS records
- Azure will create
-
If the VNet is linked to a Private DNS Zone:
- It will force resolution to an internal IP
-
If not linked:
- It will still use the public IP Simple judgment:
-
Different resolution results on the same machine → Different DNS path
-
Two different results for the same domain → DNS override occurred
Additional Notes
- Private DNS Zone only takes effect when linked to a VNet (a common missed configuration)
- Azure Web App can still be affected by DNS even without VNet Integration
- It’s normal for the same domain to resolve differently in different environments, it’s not a bug
Wrap-up
The IP tells you which path you’re taking; stop guessing the network, DNS is the key.
Troubleshooting Web App DNS Resolution (Public / Private Switching)
https://joyceowo.github.io/posts/en/343a78ea09fa809f97d2c221d3e00135/