Configuring ISAPI Extensions (IIS 6.0)

By adjusting several settings that are associated with the ISAPI extensions (ISAPI DLLs) that run on your server, you can fine-tune server performance. Logging usage data, such as the number of requests and the time they were made, can help you determine how to make the adjustments.


To help minimize the attack surface of the server, IIS 6.0 is not installed on Windows Server 2003 by default. When you first install IIS 6.0, it is locked down -- which means that only request handling for static Web pages is enabled, and only the World Wide Web Publishing Service (WWW service) is installed. None of the features that sit on top of IIS are turned on, including ASP, ASP.NET, CGI scripting, FrontPageŽ 2002 Server Extensions from Microsoft, and WebDAV publishing. If you do not enable these features, IIS returns a 404 error. You can enable these features through the Enabling Web Service Extensions node in IIS Manager. For more information about how to troubleshoot 404 errors and other issues, see Troubleshooting IIS 6.0.

Caching ISAPI extensions

ISAPI DLLs can be loaded and cached so that additional requests can be processed without calling them again. Otherwise, the DLLs are unloaded after they are run. Caching reduces the time a user waits for a DLL to load, and most ISAPI extensions benefit from caching. You should clear this option only for special circumstances, such as debugging ISAPI extensions.


You must be a member of the Administrators group on the local computer to perform the following procedure or procedures. As a security best practice, log on to your computer by using an account that is not in the Administrators group, and then use the runas command to run IIS Manager as an administrator. At a command prompt, type runas /User:Administrative_AccountName"mmc %systemroot%\system32\inetsrv\iis.msc".

To enable caching


In IIS Manager, expand the local computer, and then click the starting-point directory of the application you want.


Right-click the directory, and then click Properties.


Click the appropriate tab: Home Directory, Virtual Directory, or Directory.


In the Application settings area, click Configuration, and then click the Mappings tab.


On the Mappings tab, select the Cache ISAPI extensions check box.

Related Information

For more information about logging server activity, see Logging Site Activity.

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