The answer is a DNS server not resolving local hostnames. This is correct because when you can ping a file server by its IP address but not by its hostname, the network connectivity is intact, but the name-to-IP translation mechanism is broken. DNS is the service responsible for that translation, so a failure to resolve local hostnames points directly to a DNS configuration or record issue. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of the OSI model’s application layer and the difference between IP-based and name-based connectivity. A common trap is to suspect a firewall or gateway problem, but since internet access works and IP pings succeed, the issue is isolated to name resolution. Remember the memory tip: “If IP works but names don’t, DNS is what you won’t.”
220-1201 Network Configuration Concepts Practice Question
This 220-1201 practice question tests your understanding of network configuration concepts. 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 their desktop computer cannot connect to any network shares, but they can access the internet. The technician pings the file server by IP address successfully, but pinging by hostname fails. Which network configuration issue is most likely causing this problem?
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
✓
The DNS server is not resolving local hostnames.
Successful ping by IP but failure by hostname indicates that the computer cannot resolve the server's name to an IP address. This points to a DNS issue, as DNS is responsible for translating hostnames to IP addresses. The internet access suggests the DNS server is reachable but may not have the correct records for the local server.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 DHCP server is not assigning a default gateway.
Why it's wrong here
If the default gateway were missing, internet access would fail, but the user can access the internet.
✗
The subnet mask is incorrect.
Why it's wrong here
An incorrect subnet mask would likely cause both local and internet connectivity issues, not just name resolution.
✓
The DNS server is not resolving local hostnames.
Why this is correct
Since IP pings work but hostname pings fail, the DNS server is not providing the correct A record for the file server, causing the resolution failure.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
If the firewall blocked ICMP, pinging by IP would also fail, but the technician succeeded with an IP ping.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 220-1201 subnetting questions on CIDR, address ranges, and subnet selection.
Network Configuration Concepts — This question tests Network Configuration Concepts — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The DNS server is not resolving local hostnames. — Successful ping by IP but failure by hostname indicates that the computer cannot resolve the server's name to an IP address. This points to a DNS issue, as DNS is responsible for translating hostnames to IP addresses. The internet access suggests the DNS server is reachable but may not have the correct records for the local server.
What should I do if I get this 220-1201 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 220-1201 subnetting questions on CIDR, address ranges, and subnet selection.
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?
CIDR notation defines the prefix length.
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