The answer is DNS, as the ability to ping external IP addresses like 8.8.8.8 confirms that the network stack, IP configuration, and routing are all functional, while the failure to load websites points directly to a breakdown in name resolution. DNS is the service responsible for translating human-readable domain names into machine-readable IP addresses; when it fails locally, the computer cannot resolve website names even though it can reach those IPs directly. On the CompTIA A+ Core 1 220-1201 exam, this scenario is a classic troubleshooting question designed to test your understanding of the OSI model’s application layer versus the network layer—ping works at Layer 3 (IP), but web browsing requires Layer 7 (DNS). A common trap is to suspect DHCP or NAT, but since other devices on the same network work fine, the issue is isolated to this computer’s DNS configuration. Remember the memory tip: “Ping by IP, fail by name—DNS is the one to blame.”
220-1101 Network Services Practice Question
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 user complains that they cannot access any websites, but they can ping external IP addresses like 8.8.8.8 successfully. Other devices on the same network work fine. Which network service is most likely failing on this user's computer?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DNS
The user can ping by IP but not access websites, indicating that name resolution is failing. DNS translates domain names to IP addresses; since other devices work, the issue is likely local to the user's DNS configuration. DHCP and NAT are network-wide and would affect all devices.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
DHCP
Why it's wrong here
DHCP assigns IP settings; the user has a valid IP and can ping, so DHCP is working.
✓
DNS
Why this is correct
DNS resolves domain names to IPs. The user can ping by IP but not by name, so DNS is likely misconfigured or not responding on that machine.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
NAT
Why it's wrong here
NAT is a router function; if it were failing, all devices would be affected, not just this one.
✗
Proxy
Why it's wrong here
A proxy server could cause this, but it's less common in small networks; DNS is the more direct cause given the symptoms.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1201 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
Network Services — This question tests Network Services — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: DNS — The user can ping by IP but not access websites, indicating that name resolution is failing. DNS translates domain names to IP addresses; since other devices work, the issue is likely local to the user's DNS configuration. DHCP and NAT are network-wide and would affect all devices.
What should I do if I get this 220-1201 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A user reports that they cannot access any websites, but they can ping the IP address of a public DNS server (8.8.8.8). What is the most likely misconfigured network service?
easy
A.DHCP
✓ B.DNS
C.NAT
D.Proxy
Why B: The ability to ping an external IP but not access websites indicates that DNS resolution is failing. DNS translates domain names to IP addresses, and without it, web browsing fails even if the internet connection is working. The DHCP server or static DNS settings should be checked.
Variation 2. A user reports that they can access internal resources using IP addresses but cannot access them using hostnames. Other users on the same network have no issues. What is the most likely cause?
medium
A.The DHCP server is out of addresses
B.The DNS server is down
✓ C.The user's DNS settings are incorrect
D.The router's NAT is misconfigured
Why C: The ability to use IP addresses but not hostnames points to a DNS resolution problem on the user's device. This could be due to a misconfigured DNS server address in the network settings or a local hosts file issue. Other users working normally suggests the problem is client-specific.
Last reviewed: Jun 18, 2026
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