Error message when you try to create a Windows SharePoint Services 3.0 Web application in SharePoint 3.0 Central Administration: "The IIS Web Site you have selected is in use by SharePoint"

In SharePoint 3.0 Central Administration, you try to create a Microsoft Windows SharePoint Services 3.0 Web application and then extend the Web application to a Microsoft Internet Information Services (IIS) Web site. When you configure the settings for the Web site, you do not assign a host header name to the Web site. However, when you click OK on the Create New Web Application page, you receive one of the following error messages:

Error message 1

Error message 2

This issue occurs if the following conditions are true:

• A Web site already exists on the same port.
• The existing Web site is not assigned a host header name.
• The existing Web site has an IP address assigned to it.

For example, this issue occurs in the following scenario:

1. In SharePoint 3.0 Central Administration, you create a Web application. Then, you extend the Web application to an IIS Web site on port 80. You do not assign a host header name to the Web site.
2. In Internet Information Services (IIS) Manager, you assign an IP address to the Web site.
3. In SharePoint 3.0 Central Administration, you try to create another Web application and then extend it to an IIS Web site on port 80. You do not assign a host header name to the Web site.

To work around this issue, follow these steps:

1. In SharePoint 3.0 Central Administration, assign a host header name to each Web application that you create that uses the same port. The host header name differentiates each Web site on the port. To assign a host header name when you create a Web application, follow these steps:
   1. Start SharePoint 3.0 Central Administration.
   2. Click Application Management, and then click Create or extend Web application under SharePoint Web Application Management.
   3. On the Create or Extend Web Application page, click Create a Web Application.
   4. On the Create a New Web Application page, specify the settings that you want for the Web application. In the IIS Web Site area, make sure that you specify the host header name in the Host Header box.
   5. Click OK.
2. After the Web site is created in IIS, use Internet Information Services (IIS) Manager to remove the host header name. Then, assign an IP address to the Web site. To do this, follow these steps:
   1. Start Internet Information Services (IIS) Manager.
   2. Expand ServerName, and then expand Web Sites.
   3. Right-click the Web site that you want to configure, and then click Properties.
   4. Click the Web Site tab, and then click Advanced.
   5. In the Advanced Web Site Identification dialog box, click the entry for the Web site, and then click Edit.
   6. Remove the host header name that appears in the Host header value box, and then assign the IP address that you want in the IP address box.
   7. Click OK three times.

The issue that is discussed in this article is an expected behavior. When you use Internet Information Services (IIS) Manager instead of SharePoint 3.0 Central Administration to change the settings of an IIS Web site, Windows SharePoint Services 3.0 is not aware of the new settings. When you stop the SharePoint Web Application service, Windows SharePoint Services 3.0 deletes the IIS Web sites from the server. When you then restart the SharePoint Web Application service, Windows SharePoint Services 3.0 re-creates the IIS Web sites based on the settings that Windows SharePoint Services 3.0 was originally aware of. You must reapply any changes to settings that you made outside SharePoint 3.0 Central Administration. These settings include changes to settings such as bindings and certificate assignments.

During the design stage for Windows SharePoint Services 3.0, it was expected that these types of changes would occur infrequently. Therefore, additional administration steps were not added to Windows SharePoint Services 3.0 administration. Unfortunately, Windows SharePoint Services 3.0 does not expose the full set of IIS bindings in the Web application creation administration pages. Specifically, Windows SharePoint Services 3.0 does not expose the IP address assignment. The reason is that while other binding are typically identical for all servers in a server farm, the IP binding is almost always unique for each server in a server farm when you want to assign such a binding. This scenario presents an issue in which Windows SharePoint Services 3.0 would have had to include a control to specify what the binding is for each server. However, the control does not fit well with the concept that each server is a clone of every other server in the server farm model.

Additionally, if you later decide to add a server to the server farm, Windows SharePoint Services 3.0 would have to provide a way to specify what the binding must be for the new server before Windows SharePoint Services 3.0 creates an IIS Web site for the Web application. During the design stage, some efforts were made to resolve this issue. However, after additional investigation, the solutions that were examined did not significantly improve the experience beyond the manual workarounds.