To connect Compute Engine instances within a Google Cloud Platform project to workloads running in a dedicated server room that can only be accessed from within the private company network, you can use the following approaches:

Cloud VPN: Cloud VPN securely connects your on-premises network to your Google Cloud Virtual Private Cloud (VPC) network through an IPsec VPN connection. This enables secure communication between your GCP instances and your on-premises workloads over the internet.

Cloud Interconnect: Cloud Interconnect provides direct physical connections between your on-premises network and Google's network. It offers higher bandwidth and lower latency compared to Cloud VPN, making it suitable for workloads that require fast and reliable connectivity.

Both Cloud VPN and Cloud Interconnect allow you to securely connect your on-premises environments to Google Cloud, ensuring that the workloads remain within the private company network.

References

Cloud VPN Overview

Cloud Interconnect Overview