AZ-104 Question 242
Single answerYou have configured a public Azure Load Balancer with two virtual machines in the backend pool. The health probe is set to monitor port 80, but clients are failing to access the application and all requests time out. Which of the following is the most likely root cause?
- A
No inbound security rule is configured in the Network Security Group to allow port 80 traffic
- B
The Load Balancer's SKU is set to Basic instead of Standard, preventing distribution of traffic
- C
The health probe is configured with an incorrect interval, causing it to fail intermittently
- D
The backend pool VMs are using ephemeral ports that conflict with the probe port
Show answer and explanation
Correct answer: A
Explanation
In this scenario, the primary issue is that the NSG lacks an inbound rule allowing port 80 traffic. Without such a rule, the Load Balancer's health probe and client connections will consistently fail, causing all requests to time out.
- A. Correct.
Correctly configured inbound rules are essential for allowing traffic through the NSG. If there is no inbound rule for port 80, the load balancer traffic cannot reach the VMs, resulting in request timeouts.
- B. Incorrect.
While Basic SKU has limitations compared to Standard, it does support distributing traffic on port 80. Merely using Basic SKU does not inherently prevent traffic distribution.
- C. Incorrect.
An incorrect interval may cause intermittent probe failures, but it typically does not result in consistent timeouts for all client requests.
- D. Incorrect.
Ephemeral ports are dynamically allocated client-side ports. They usually do not conflict with a well-defined health probe port such as port 80.