IssueTracker

As of today, it is only possible to have one range of Private IP ranges associated within the same Shared VPC network. In other words, as of today, you can have only one range of private IP for a MySQL Cloud SQL instance, another one for PostgreSQL Cloud SQL instance, and another one more for MySQLServer Cloud SQL instance within the same network.


Problem you have encountered:

It is not possible to have 2 different private IP ranges for a Cloud SQL instance using the same shared VPC.

What you expected to happen:

To have a dropdown or a select box inside your Cloud SQL instance when you are spinning it up for the first time, in order to choose between one or more different private IP ranges, inside the same Shared VPC.
 
Other information (workarounds you have tried, documentation consulted, etc):

The recommended solution is to create a different network for every private IP range you would like you have. In other words, create as many networks as ranges of private IP you would like to have.