DotNetNuke supports multiple portals from a single database/codebase. It accomplishes this by converting the URL of the client browser Request to a valid PortalID in the Portals database table. The following steps describe the process:

1. Web Server Processing

When a web server receives a Request from a client browser, it compares the file name extension on the target URL resource to its Application Extension Mappings defined in IIS.
Based on the corresponding match, IIS then sends the Request to the defined Executable Path ( aspnet_asapi.dll in the case of ASP.NET Requests ).
The aspnet_isapi.dll engine processes the Request in an ordered series of events beginning with Application_BeginRequest.
 
2. Application_BeginRequest ( Common.Globals.asax.vb )

The Request URL is parsed based on the "/" character
A Domain Name is constructed using each of the relevant parsed URL segments.

Examples:

URL: http://www.domain.com/default.aspx = Domain Name: www.domain.com
URL: http://209.75.24.131/default.aspx = Domain Name: 209.75.24.131
URL: http://localhost/DotNetNuke/default.aspx = Domain Name: localhost/DotNetNuke
URL: http://www.domain.com/virtualdirectory/default.aspx = Domain Name: www.domain.com/virtualdirectory
URL: http://www.domain.com/directory/default.aspx = Domain Name: www.domain.com/directory

Using the Domain Name, the application queries the database ( Portals table - PortalAlias field ) to locate a matching record.

Note: If there are multiple URLs which correspond to the same portal then the PortalAlias field must contain each valid Domain Name in a comma seperated list.

Example:

URL: http://localhost/DotNetNuke/default.aspx
URL: http://MACHINENAME/DotNetNuke/default.aspx
URL: http://209.32.134.65/DotNetNuke/default.aspx
PortalAlias: localhost/DotNetNuke,MACHINENAME/DotNetNuke,209.32.134.65/DotNetNuke

Note: If you are installing the application to a remote server you must modify the PortalAlias field value for the default record in the Portals table according to the rules defined above.