>Hello,
>
>we develop in .NET 3.5 Visual Studio 2008 and use MS SQL Server 2008.
>Up to now we connect to the SQL Server via a normal connection string and a native connection via TCP/IP.
>Now we have a SQL 2008 Server Cluster, with currently two machines.
>My question is now, how we should access the SQL Cluster?
>Our administrator told us to use a ODBC connection now, as the ODBC driver handles the fail over switching automatically.
>Is ODBC the way to go, or is the fail over thing also possible with a native connection?

If you're currently connecting to an IP address e.g. \\192.168.x.x\SomeInstanceName you will need to connect to the cluster's instance name, instead. To clients, the cluster appears as a single instance:

http://msdn.microsoft.com/en-us/library/ms189134.aspx

The SQL Native Client is newer than ODBC, I'd be surprised if it wouldn't handle failover properly (n.b. I don't have any direct experience with this). Nonetheless, if your admin tells you to use ODBC, it's probably a good idea to listen ;)