AZ-104 Question 241
Single answerYou are an Azure Administrator for an e-commerce application that uses an Azure Load Balancer to distribute HTTP traffic across multiple backend virtual machines. The Load Balancer is configured with a TCP-based health probe on port 80 and set to a 5-second interval. Some customers occasionally report timeouts, and application logs do not show any corresponding requests on the VMs. You have confirmed that all Network Security Group (NSG) rules allow inbound traffic on port 80. Which action is the most appropriate next step to troubleshoot the load balancing issue?
- A
Switch the health probe to an HTTP-based probe on port 80 and specify a valid health probe path.
- B
Lower the idle timeout setting to 3 minutes on the Load Balancer.
- C
Deploy an Azure Application Gateway in front of the existing Load Balancer to inspect traffic at the application layer.
- D
Enable session persistence (Source IP affinity) for the Load Balancer.
Show answer and explanation
Correct answer: A
Explanation
When troubleshooting timeouts and missing log entries, verifying the actual HTTP responses is critical. By switching to an HTTP-based health probe, the Load Balancer can detect if the backend VMs are truly responding at layer 7 rather than simply listening on the TCP port. This helps pinpoint issues where the service on the VM may not be processing requests correctly despite the TCP port being open.
- A. Correct.
Using an HTTP-based health probe ensures that the Load Balancer validates the actual HTTP response from the application, not just the open TCP port. This can help identify issues when the underlying service on the VM is not responding correctly on the HTTP level.
- B. Incorrect.
Decreasing the idle timeout setting alone does not address the root cause of intermittent timeouts, especially when the application logs show no corresponding requests.
- C. Incorrect.
Deploying an Application Gateway might help with more advanced diagnostics or application-level routing, but it is not the most immediate step for troubleshooting basic health probe issues.
- D. Incorrect.
Enabling session persistence (affinity) is useful for scenarios requiring user sessions to stick to a specific VM, but it does not address missing requests in the application logs or verify correct HTTP responses.