Communicating with Multiple Instances
Each instance of Microsoft® SQL Server™ 2000 listens on a unique set of network address so that applications can connect to different instances. SQL Server 2000 clients do not have to be configured to connect to an instance of SQL Server 2000. The SQL Server 2000 client components query a computer running instances of SQL Server 2000 to determine the Net-Libraries and network addresses for each instance. The client components then transparently choose a supported Net-Library and address for the connection without having to be configured on the client. The only information the application must supply is the computer name and instance name. For more information, see Controlling Net-Libraries and Communications Addresses.
A default instance of SQL Server 2000 listens on the same network addresses as earlier versions of SQL Server; therefore, applications using the client connectivity components of SQL Server version 7.0 or earlier can continue to connect to the default instance with no change. Named instances listen on alternative network addresses, and client computers using the client connectivity components of SQL Server version 7.0 or earlier must be set up to connect to the alternative addresses.