Allocated IP address changed on web app service - Azure allocated domains failed as well.

Robert Graham 0 Reputation points


I have been hosting on Azure for a little over 14 years now. As part of that hosting is a set of web app services that have been running for 99% of that time.

All of these web apps sat on the same web app service plan and resource group and as a result all had the same IP address assigned to them for use with DNS entries for A records etc.

However, most of these apps were running under CNAME records so the DNS entries where pointing to the Azure assigned domain e.g. ????

Starting yesterday (2024-06-12) I started to see some intermittent web site failures – uptime robot was saying they were up but I was seeing them down. After around 2 hours everything seemed to resolve itself without need for me to change anything in regard to the deployments or settings.

Today was a totally different matter. All sites went down without warning.

When I tried running tracert and other tools the route was simply timing out. I knew it was DNS related because when I stopped the services in Azure I did not get to the This Web App is stopped message and blue screen.

On further investigation I noticed that the IP address of the web apps had changed from a single IP starting 40.??.??.??, to two IP addresses separated with a comma.

This was strange as I had not seen two IP addresses listed in this field in 14 years.

It was also no good to me because as already stated most of the DNS set up was pointing to the Azure domains for CNAME config. The IP address that the azure domains mapped to was the old IP address and not either of new ones it was showing me and as a result it was not found - therefore my entire IT set up was left pointing to nothing. I confirmed this by running IP lookups and other common tasks.

Not only could I not get any of my sites to work but none of the features like App Service Editor or Advanced Tools would open or operate because Azure couldn’t even see their own sites.

I have spent the entire day and no doubt some of this evening creating new app service plans, app services and all the associated config around to ensure my paying clients were not offline. I’ve had better days!

Has anyone experienced this situation and why would it have happened.

Europe North was where the services were deployed to.


Azure App Service
Azure App Service
Azure App Service is a service used to create and deploy scalable, mission-critical web apps.
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