During database migration, the destination Cloud SQL database needs to connect
to the source database. Database Migration Service provides several ways to configure
this connectivity. The connectivity method you choose depends on the type of
source database, and whether it resides on-premises, in Google Cloud, or in another
There are three types of connectivity methods that you can configure:
IP allowlists: Choose this method if you want to use public connectivity.
Reverse SSH tunnel using a cloud-hosted VM: Choose this method if you want to use secure connectivity, and when you don't have a virtual private cloud (VPC) network in Google Cloud from which you can reach the source database.
VPC peering: Choose this method if you want to use private connectivity, and when you have a VPC network in Google Cloud from which you can reach the source database. Use VPC peering if you have a VPN or Cloud Interconnect connection set up in Google Cloud.