Unable to join an ArcGIS Server machine with a different .NET Extension Support feature

Description

When attempting to join an ArcGIS Server machine with a different .NET Extension Support feature, the following error is returned:

Error:
Failed to join the site <site1URL>. The state of the .NET Extension Support feature configured on machine <Site2URL> does not match the site running at <Site1URL>. All machines in a site are required to have the same .NET Extension Support configuration.

Cause

The .NET Extension Support configuration on the original ArcGIS Server machine does not match the configuration on the new machine being added to the site.

Solution or Workaround

Ensure that the .NET Extension Support feature on the new ArcGIS Server machine matches the configuration of the existing server before joining it to the site.

1. Click Start on the new ArcGIS Server machine.
2. Type Control Panel in the search bar and click Control Panel > Programs > Programs and Features.
3. Right click ArcGIS Server 11.x and select Change > Modify.
4. On the .NET Extension Support drop-down list, select This feature, and all subfeatures, will be installed on local hard drive.
5. Click Next > Install.

6. Once the installation has been updated, proceed to join the site. Refer to ArcGIS Server: Join an existing site for instructions.