Google Cloud Professional Cloud Architect — Question 43

You set up an autoscaling instance group to serve web traffic for an upcoming launch. After configuring the instance group as a backend service to an HTTP(S) load balancer, you notice that virtual machine (VM) instances are being terminated and re-launched every minute. The instances do not have a public IP address.
You have verified the appropriate web response is coming from each instance using the curl command. You want to ensure the backend is configured correctly.
What should you do?

Answer options

• A. Ensure that a firewall rules exists to allow source traffic on HTTP/HTTPS to reach the load balancer.
• B. Assign a public IP to each instance and configure a firewall rule to allow the load balancer to reach the instance public IP.
• C. Ensure that a firewall rule exists to allow load balancer health checks to reach the instances in the instance group.
• D. Create a tag on each instance with the name of the load balancer. Configure a firewall rule with the name of the load balancer as the source and the instance tag as the destination.

Correct answer: C

Explanation

The correct answer is C because load balancer health checks need to reach the instances to determine their status. Without the appropriate firewall rule allowing these health checks, the instances may be marked as unhealthy, causing them to be terminated and relaunched. Options A and B do not address the specific issue of health checks, while option D incorrectly focuses on tagging rather than the necessary health check access.