Sql-server – SQL Server 2012 Availability Group is it “AlwaysON”

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.

You have to do following :

1. Drop the availability group then
2. using regedit, (first backup the registry of old availability group that starts with HKEY_LOCAL_MACHINE\Cluster\HadrAgNameToldMap) and then delete that key and
3. Finally create a new Availability Group with new name.

Note: Extra Caution .. as you are dealing with Windows Registry, Back it up first