Im not a big clustering/HA expert, but I obviously understand the need for such things to exist

However, the standard SQL tooling, SSMS etc, seems to go out of its way to make the MultiSubNetFailover option as inaccessible and convoluted as possible.  Quite why this option even exists and its not done as default escapes me, clients should be entirely agnostic to the server its talking to.

After going through this pain again, this time deploying SSIS packages to an AG, i stumbled over this msdn blog

https://blogs.msdn.microsoft.com/alwaysonpro/2015/12/01/improved-multisubnet-listener-behavior-with-newly-released-sql-client-provider-in-net-4-6-1/

So .NET 4.6.1 does default to MultiSubNetFailover = True, which is great.

There is a rather cryptic note on the end though

“Note that this isn’t what ended up being shipped.  Instead a new default property TransparentNetworkIPResolution was introduced to SqlConnection.”

Ive asked for some clarification on what that exactly means, im unable to find any other reference to that property, but In my testing the effect seems to be the same :S

So,  if you have MultiSubNetFailOver=True pain,  give .NET 4.6.1 a whirl,  it should resolve that.