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CV0-004 Practice Question: Refer to the exhibit

Exhibit

[2025-01-20 14:23:45] ERROR Backend "web-svr-01" health check failed (HTTP 502)
[2025-01-20 14:23:46] ERROR Backend "web-svr-02" health check failed (HTTP 502)
[2025-01-20 14:23:47] ERROR Backend "web-svr-03" health check failed (HTTP 502)

Refer to the exhibit. A cloud load balancer is returning 502 Bad Gateway errors to clients. What is the most likely cause?

⚠ Common exam trap

CompTIA often tests the distinction between HTTP status codes (502 vs. 504 vs. 503) and their root causes, trapping candidates who confuse a backend response failure (502) with a timeout (504) or an overload condition (503).

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The backend web servers are not responding correctly.

A 502 Bad Gateway error indicates that the load balancer (acting as a proxy or gateway) received an invalid or no response from the upstream backend web servers. This typically occurs when the backend servers are overloaded, have crashed, or are misconfigured (e.g., incorrect health check path, application pool failure). The load balancer successfully forwards the request but fails to get a valid HTTP response, triggering the 502 error.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    The load balancer's SSL certificate is invalid.

    Why it's wrong here

    An invalid SSL certificate would cause HTTPS errors, not 502 health check failures.

  • ✗

    The security group allows inbound traffic from the load balancer.

    Why it's wrong here

    If security groups were blocking, health checks would fail with a timeout, not 502.

  • ✗

    The DNS record points to the wrong IP.

    Why it's wrong here

    DNS issues would prevent clients from reaching the load balancer, not cause 502 errors from the load balancer.

  • ✓

    The backend web servers are not responding correctly.

    Why this is correct

    502 errors and health check failures indicate the backend servers are not serving correctly.

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This CV0-004 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CV0-004 exam.