SharePoint 2019 Extending Web Application Breaks Sites

Stuart Hilbert 0 Reputation points

I am trying to extend a SharePoint 2019 Web Application in order to support SSO through Entra App Proxy.

When I extend my SharePoint 2019 Web Application I can see that a new site is created in IIS, however, both my current SharePoint 2019 Site and my new extended SharePoint 2019 are broken.

Looking at the console in Chrome reveals a ton of Javascript errors.

I have found that if I remap all of the virtual directories in both the current and new IIS site I can get them to bring up my SharePoint site.

However, there are some remaining issues.

  1. On the main SharePoint Site, when I navigate to "Site Settings", I get a 401 error. However, on other sites within the same Site Collection I can get to "Site Settings" without an issue.
  2. As I go deeper into the main SharePoint Site structure, sites start to exhibit additional js file missing errors that seem like they should be available looking at IIS.

From what I can tell Extending a SharePoint Web Application shouldn't result in anything breaking and should be fairly automatic.

This SharePoint installation has bene around a long time and has been upgraded from at least SharePoint 2013 and likely has some gremlins in it.

Do you have any suggestions how to get the Extend feature working?

Thank You!

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SharePoint Server Management
SharePoint Server Management
SharePoint Server: A family of Microsoft on-premises document management and storage systems.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Emily Du-MSFT 42,506 Reputation points Microsoft Vendor

    What is the authentication method of the web application?

    Check whether following lines are missing in the web configuration file of the web application.

    <authentication mode="Forms">

    <forms loginUrl="/_login/default.aspx" />


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  2. Stuart Hilbert 0 Reputation points

    I can't emphasize enough, how extending the web application in SharePoint completely breaks the main SharePoint site.

    Many of the virtual directories are remapped in IIS.