Troubleshooting External Access Issues on Google Cloud Platform: A Beginner’s Guide

If you’re new to Google Cloud Platform (GCP) and recently encountered difficulties accessing your application externally, you’re not alone. Many newcomers find navigating GCP’s interface challenging, especially when trying to configure access settings for their deployed apps. This guide aims to help you understand common issues and steps to troubleshoot external connectivity problems on GCP.

Scenario Overview

Suppose you’ve deployed an application on GCP, and after enabling certain features—perhaps related to user access or network settings—you notice that your app is no longer accessible from outside your project. Such issues can be frustrating, but with a methodical approach, you can identify and resolve the problem.

Common Causes for External Access Failures

1. Firewall Rules: GCP uses firewall rules to control incoming and outgoing traffic. If modifications are made without updating these rules, external access might be blocked.
2. Service Configuration: Certain services or load balancer settings might restrict access or require specific configurations to allow external traffic.
3. IAM & Access Controls: Privilege settings may restrict access to certain resources or endpoints.
4. Network Settings: Incorrect VPC or subnet settings can also impede external connectivity.

Step-by-Step Troubleshooting

1. Check Firewall Rules
2. Navigate to the VPC Network section within the Google Cloud Console.
3. Select Firewall Rules.
4. Ensure there’s a rule allowing inbound traffic on the port your app is listening on (e.g., port 80 or 443).

5. If unsure, create a new rule allowing TCP traffic on the required ports from 0.0.0.0/0 (all IPs), but be cautious to avoid exposing your app unnecessarily.

6. Verify Service Exposure

7. Confirm that your deployment (e.g., Cloud Run, Compute Engine, App Engine) is set to be accessible externally.
8. For Cloud Run:
   • Check the deployment settings to ensure it is set to Allow unauthenticated invocations.
   • You can typically find this in the Cloud Run service details.

9. For other services, review the configuration to confirm external access is enabled.

10. Inspect Network Settings

11. Review your Virtual Private Cloud (VPC) configurations.

12. Ensure that your network settings aren’t blocking external incoming traffic.

13. Review Deployment Details

14. Verify the application URL