Always On Client Connectivity (SQL Server)

This topic describes considerations for client connectivity to AlwaysOn Availability Groups, including prerequisites, restrictions, and recommendations for client configurations and settings.

Client Connectivity Support

The section below provides information about Always On Availability Groups support for client connectivity.

Driver Support

The following table summarizes driver support for Always On Availability Groups:

Driver Multi-Subnet Failover Application Intent Read-Only Routing Multi-Subnet Failover: Faster Single Subnet Endpoint Failover Multi-Subnet Failover: Named Instance Resolution For SQL Clustered Instances
SQL Native Client 11.0 ODBC Yes Yes Yes Yes Yes
SQL Native Client 11.0 OLEDB No Yes Yes No No
ADO.NET with .NET Framework 4.0 with connectivity patch***** Yes Yes Yes Yes Yes
ADO.NET with .NET Framework 3.5 SP1 with connectivity patch ** Yes Yes Yes Yes Yes
Microsoft JDBC driver 4.0 for SQL Server Yes Yes Yes Yes Yes

* Download the connectivity patch for ADO .NET with .NET Framework 4.0:

** Download the connectivity patch for ADO.NET with .NET Framework 3.5 SP1:


To connect to an availability group listener, a client must use a TCP connection string.

Related Tasks

See Also

Overview of AlwaysOn Availability Groups (SQL Server)
Failover Clustering and AlwaysOn Availability Groups (SQL Server)
Prerequisites, Restrictions, and Recommendations for AlwaysOn Availability Groups (SQL Server)
Availability Group Listeners, Client Connectivity, and Application Failover (SQL Server)
About Client Connection Access to Availability Replicas (SQL Server)
Microsoft SQL Server AlwaysOn Solutions Guide for High Availability and Disaster Recovery
SQL Server AlwaysOn Team Blog: The official SQL Server AlwaysOn Team Blog
A long time delay occurs when you reconnect an IPSec connection from a computer that is running Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, or Windows Server 2008 R2
The Cluster service takes about 30 seconds to fail over IPv6 IP addresses in Windows Server 2008 R2
Slow failover operation if no router exists between the cluster and an application server