Connect Google Cloud SQL instance to external replica via VPN

Question

We have a (route based) VPN between our data center and Google Cloud. I'm trying to set up a replica of one of our on-prem databases in Google Cloud.

With current setup, Google Cloud SQL instance is unable to communicate with our on-prem instance via local IP through VPN tunnel because (my understanding is) no routes exist from the sub-network on which Cloud SQL instance is placed by Google.

Will this work with Cloud Router?

Is the only option is exposing our on-prem DB to the internet to get this working?

Answer 1

Based from this link Cloud router is needed to connect to external source. This is to advertise all subnet that are visible to the cloud router. You can check the link for more information.

Regarding exposing your DB to the internet, not necessarily and that is not the only option if you like to connect your on-prem DB to the Google cloud network your idea of cloud VPN will also do since VPN tunnel is a secure connection between on-prem network and Google cloud network.