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Creating a Valid Connection String Using VIA Protocol

To create a valid connection string using Virtual Interface Adapter (VIA), you must provide each of the following elements:

  • Specify an Alias Name.
  • Provide the network interface card (NIC) number followed by a port number in the Via Parameters box. If left blank, VIA will attempt to connect to port <NIC#>:1433.
  • Specify VIA as the Protocol.
  • In the Server field, enter the server name or <servername>\<instancename> for a named instance.

At the time of connection, the SQL Native Client component reads the Server, Protocol, and Via Parameters values from the registry for the specified Alias Name, and creates a connection string in the format via:<servername> [\instancename],<nic number>:<port>.

When two or more instances of Microsoft SQL Server are installed on the same computer, VIA connections can be ambiguous. When enabled, the VIA protocol attempts to use the TCP/IP settings, and listens on port 0:1433. For VIA drivers that do not allow configuration of the port, both instances of SQL Server will be listening on the same port. Incoming client connections can receive a connection to the correct server instance, the incorrect server instance, or be denied a connection, because the port is in use.

The following query will return the protocol used for the current connection.

SELECT net_transport 
FROM sys.dm_exec_connections 
WHERE session_id = @@SPID;

Connecting by server name:

Alias Name         ServerAlias
Via Parameters     0:1433
Protocol           VIA
Server             <servername>

Connecting to a named instance by server name:

Alias Name         ServerAlias
Via Parameters     0:1433
Protocol           VIA
Server             <servername>\<instancename>

To specify the network protocol as a sqlcmd parameter, search Books Online for the topic How to: Connect to the Database Engine Using sqlcmd.exe.