You are routing all your internet facing traffic from Google Cloud through your on-premises internet...

Configure Cloud Interconnect:

Cloud Interconnect provides high-bandwidth, low-latency connectivity between your on-premises network and Google Cloud. You can choose between Dedicated Interconnect or Partner Interconnect depending on your requirements.

Set up the physical connection and establish the interconnect through the Google Cloud Console or by working with a partner.

Set Up HA VPN:

High Availability (HA) VPN provides a robust, reliable VPN connection to Google Cloud with SLA guarantees. This is crucial for ensuring secure and high-bandwidth connectivity.

Configure two VPN tunnels to ensure redundancy and failover capabilities.

Update Default Route:

Replace the default 0.0.0.0/0 route in your Google Cloud VPC to direct traffic to your on-premises network via the Cloud Interconnect and HA VPN setup.

This ensures all internet-facing traffic is securely routed through your on-premises internet connection.

Ensure Proper Security and Routing Policies:

Implement appropriate firewall rules and security policies on both Google Cloud and on-premises environments to control traffic and ensure secure communication.

Monitor the traffic and connectivity status to maintain optimal performance and security.