ASP Authentication Providers in MOSS

ASP.NET 2.0 enables administrators and programmers to define multiple ways to authenticate users. This is done through so-called authentication providers.

Foreach IIS web application a programmer can use a different authentication provider, configured in his/hers web.config file of the application.

Because SharePoint, MOSS 2007, is ented on top of ASP.NET 2.0, you can also use multiple ways of authentication. This is done per SharePoint Web Application. When you want to have multiple ways of authentication within one SharePoint web application, you have to extend the web application across multiple IIS web sites. Each extensions of the web application will be placed in a specific zone.

For instance, you want to extend the web application towards the internet for external users(external.portal.mycompany.com). In this extensions you want to use form based authentication on top of a SQL database with the user base.
On the other hand, you want to have an internal extension (internal.portal.mycompany.com). Here you specify the standard windows authentication (is standard provided).
So, in this example you can have two ways of authentication towards the same SharePoint web application. Take in notice that you have two web.config per web application for each front-end server.

To accomplish this, Microsoft SharePoint Product group has written a kind of manual how to configure multiple authentication, see link below:
http://blogs.msdn.com/sharepoint/archive/2006/08/16/702010.aspx

Cheers.