Quick Answer
The answer is that the container's port 80 is not published to the host. This is because the administrator ran `docker run -d nginx` without the `-p` or `--publish` flag, which means Docker port publishing was never configured, so no port mapping exists between the container and the host network interface. While the container is reachable via its own internal IP due to Docker's default bridge networking, the host's IP on port 80 remains unbound, causing the curl to fail. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding that `-p` is required to expose container ports externally—a common trap is assuming a running container is automatically accessible from the host. Remember the memory tip: "No publish, no host access"—if you omit `-p`, the container stays isolated to its own network.
This XK0-005 practice question tests your understanding of scripting, containers and automation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator runs the commands shown in the exhibit. The container is accessible via curl using the container IP. However, the administrator cannot access the web server using the host's IP address on port 80. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The container's IP address is incorrect.
Why wrong: The IP 172.17.0.2 is correct and accessible via curl.
The container's port 80 is not published to the host.
No -p option was used; port is only accessible on the container's network.
Nginx is configured to listen on a different port.
Why wrong: The exec command shows listen 80.
The container is not running.
Why wrong: The STATUS shows 'Up 10 minutes', so it is running.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The container's port 80 is not published to the host.
Option B is correct because the administrator ran `docker run -d nginx` without the `-p` or `--publish` flag, which means port 80 inside the container is not mapped to any port on the host. The container is accessible via its own IP because Docker networking allows direct container-to-container communication, but the host's IP on port 80 remains unbound, so curl to the host IP fails. Publishing the port with `-p 80:80` would expose the container's port 80 on the host's interface.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The container's IP address is incorrect.
Why it's wrong here
The IP 172.17.0.2 is correct and accessible via curl.
The container's port 80 is not published to the host.
Why this is correct
No -p option was used; port is only accessible on the container's network.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Nginx is configured to listen on a different port.
Why it's wrong here
The exec command shows listen 80.
The container is not running.
Why it's wrong here
The STATUS shows 'Up 10 minutes', so it is running.
Common exam traps
The trap here is that candidates assume a running container with a working service is automatically accessible on the host's IP, but Docker requires explicit port publishing to bridge the host network namespace to the container's network namespace.
Trap categories for this question
Command / output trap
The exec command shows listen 80.
Detailed technical explanation
When a container is started without port publishing, Docker assigns it an internal IP on a bridge network (typically 172.17.0.0/16), and the container's ports are only accessible from other containers on the same bridge or from the host via the container IP. The host's own IP (e.g., 192.168.1.10) does not automatically forward traffic to the container; explicit port mapping using `-p` or `--publish` creates iptables DNAT rules to redirect host traffic to the container's port. In production, this is critical for services like web servers that must be reachable from outside the Docker host.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the XK0-005 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Scripting, Containers and Automation — study guide chapter
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FAQ
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — Read the scenario before looking for a memorised answer..
The correct answer is: The container's port 80 is not published to the host. — Option B is correct because the administrator ran `docker run -d nginx` without the `-p` or `--publish` flag, which means port 80 inside the container is not mapped to any port on the host. The container is accessible via its own IP because Docker networking allows direct container-to-container communication, but the host's IP on port 80 remains unbound, so curl to the host IP fails. Publishing the port with `-p 80:80` would expose the container's port 80 on the host's interface.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This XK0-005 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 XK0-005 exam.
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