The EnableCrossAppRedirects property value is set using the enableCrossAppRedirects attribute of the forms configuration element.
The EnableCrossAppRedirects property is checked within the RedirectFromLoginPage method when the redirect URL does not point to a page in the current application. If EnableCrossAppRedirects is true, then the redirect is performed; if EnableCrossAppRedirects is false, the browser is redirected to the page defined in the DefaultUrl property.
When performing redirects across applications, you must ensure that several of the attributes in the forms configuration element are duplicated across the authenticated applications. For more information and an example, see Forms Authentication Across Applications.