- A
DNS
Why wrong: Internal websites work, so DNS is resolving internal names; external DNS might be failing, but the proxy server handles DNS for external requests, so the issue is more likely the proxy itself.
- B
DHCP
Why wrong: DHCP is working because users have IP addresses and can access internal resources.
- C
Proxy server
The proxy server is responsible for forwarding external requests. If it is down or misconfigured, users cannot reach external sites while internal access remains unaffected.
- D
NAT
Why wrong: NAT is typically handled by the router; if NAT were failing, internal access might also be affected, and the proxy often uses NAT for outbound traffic.
Question 576 of 1,020
Proxy Server Failure: Internal Sites Work, External Don't
This 220-1201 practice question tests your understanding of network services. 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.
A company uses a proxy server for internet access. Users report that they can access internal websites but cannot reach external sites. The proxy server's IP is configured in the browser settings. Which network service is most likely failing?
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.
Quick Answer
The answer is the proxy server itself, as it is the network service most likely failing when internal sites work but external ones do not. A proxy server acts as an intermediary for all outbound internet requests, so if users can reach internal resources—which typically bypass the proxy—but cannot load external websites, the proxy server or its internet-facing connection has failed. DNS and DHCP are functioning correctly because internal name resolution and IP addressing are intact. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of how proxy servers route traffic and the symptom of a broken intermediary. A common trap is to suspect DNS first, but remember: internal access proves DNS works, so focus on the proxy. Memory tip: “Internal fine, external blind—proxy’s the bottleneck you’ll find.”
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
✓
Proxy server
The proxy server is configured in the browser settings, but users can reach internal websites (which bypass the proxy) while failing to reach external sites (which require the proxy). This indicates the proxy server itself is not functioning or unreachable, as it is the designated intermediary for external traffic. DNS, DHCP, and NAT would affect both internal and external access if they were failing, so the proxy server is the most likely culprit.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DNS
Why it's wrong here
Internal websites work, so DNS is resolving internal names; external DNS might be failing, but the proxy server handles DNS for external requests, so the issue is more likely the proxy itself.
- ✗
DHCP
Why it's wrong here
DHCP is working because users have IP addresses and can access internal resources.
- ✓
Proxy server
Why this is correct
The proxy server is responsible for forwarding external requests. If it is down or misconfigured, users cannot reach external sites while internal access remains unaffected.
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.
- ✗
NAT
Why it's wrong here
NAT is typically handled by the router; if NAT were failing, internal access might also be affected, and the proxy often uses NAT for outbound traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between a proxy server failure and a DNS failure, where candidates mistakenly think DNS is the issue because external sites fail, but the key clue is that internal sites are accessible, which would not be the case if DNS were broken.
Detailed technical explanation
How to think about this question
Proxy servers operate at the application layer (Layer 7) and can be configured to forward requests for external resources while allowing direct access to internal resources. When a proxy fails, clients may still reach internal sites because those requests are often sent directly without going through the proxy, whereas external requests are explicitly routed through the proxy and fail. In enterprise environments, proxy auto-config (PAC) files or explicit browser settings control this behavior, and a common troubleshooting step is to check the proxy server's service status, firewall rules, or connectivity to the internet.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Visual reference
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Network Services — This question tests Network Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Proxy server — The proxy server is configured in the browser settings, but users can reach internal websites (which bypass the proxy) while failing to reach external sites (which require the proxy). This indicates the proxy server itself is not functioning or unreachable, as it is the designated intermediary for external traffic. DNS, DHCP, and NAT would affect both internal and external access if they were failing, so the proxy server is the most likely culprit.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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