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CV0-004 Practice Question: A load balancer log entry shows the above for a…
Exhibit
Refer to the exhibit. User-Agent: Mozilla/5.0 Status: 504 Gateway Timeout Upstream: 10.0.1.25:8080 Response Time: 30.001s
A load balancer log entry shows the above for a request. What is the MOST likely cause of the 504 error?
⚠ Common exam trap
CompTIA often tests the distinction between 502 (bad gateway, often DNS or upstream connection failure) and 504 (gateway timeout, upstream response delay), and candidates mistakenly attribute 504 errors to health check failures or DNS issues.
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 server took too long to respond to the request.
A 504 Gateway Timeout error from a load balancer indicates that the load balancer sent the request to a backend server but did not receive a timely response. The load balancer has a configured timeout value (often 30-120 seconds), and if the backend server fails to respond within that window, the load balancer terminates the connection and returns a 504. This is the most common cause of 504 errors in load-balanced environments.
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 DNS resolution for the domain name has failed.
Why it's wrong here
DNS failure prevents the client reaching the load balancer at all, yielding name-resolution errors rather than an HTTP 504 from the proxy. DNS troubleshooting is correct when clients cannot resolve the hostname, not when the load balancer reports a backend timeout.
- ✓
The backend server took too long to respond to the request.
Why this is correct
A 504 Gateway Timeout occurs when the load balancer's upstream connection to the backend exceeds its configured timeout window, so the proxy abandons the request. This matches the stem's constraint: the log records a 504, which specifically indicates backend response latency rather than connection refusal or DNS failure.
- ✗
The requested resource does not exist on the backend server.
Why it's wrong here
A missing resource returns 404 from the backend, which the load balancer forwards; a 504 indicates the backend accepted the connection but never responded within the timeout. 404 diagnosis applies when logs show the origin replying with a not-found status.
- ✗
The load balancer's health check is misconfigured.
Why it's wrong here
A 504 means the load balancer waited for a backend response and timed out; a misconfigured health check would instead remove the node from rotation, producing 502 or 503. Health checks are the right fix when healthy backends are wrongly marked down.
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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.