SQL Server 2012, Network for: AlwaysOn Availability Group with AlwaysOn AlwaysOn Failover Cluster Instances Setup: I have two data centers. In site1, my primary site, I'd like to deploy an AlwaysOn Failover Cluster Instance (FCI). In site2, my data recovery site, I'd like to deploy a single-node instance of SQL. I'd then like to use AlwaysOn Availability Groups (AG) to replicate data between site1 and site2.

I've read a lot of blog posts and TechNet articles. It's clear to me that automatic fail over is not supported for AGs with FCI members [1]. It's also clear that FCIs support nodes on multiple subnets [2]. Apparently this is achieved by updating the Virtual Network Name (VNN) in DNS. 

Question: Do AGs support multiple subnets, or do I need a spanned subnet between site1 and site2? I haven't been able to find any sources that explicitly make that clear. 

References:

[1] Failover Clustering and AlwaysOn Availability Groups (SQL Server)
http://msdn.microsoft.com/en-us/library/ff929171.aspx

[2] AlwaysOn Failover Cluster Instances (SQL Server)
http://msdn.microsoft.com/en-us/library/ms189134.aspx
Yes AG support multiple subnets as described here. Also make sure that your data provider supports MultiSubnetFailover .. .NET Framework 4 supports it.

To answer your question ... 

IF you use .NET framework 4 or 3.5 then the provider will support it as described here.

Also, a good reference to SQL Server Multi-Subnet Clustering is well documented.

With legacy client libraries or third party data providers, you cannot use the MultiSubnetFailover parameter in your connection string. To help ensure that your client application works optimally with multi-subnet FCI in SQL Server 2012, try to adjust the connection timeout in the client connection string by 21 seconds for each additional IP address. This ensures that the client’s reconnection attempt does not timeout before it is able to cycle through all IP addresses in your multi-subnet FCI.