The answer is ARP, or Address Resolution Protocol, because when pinging a device on the same subnet, the computer must resolve the target IP address to its corresponding MAC address before any data can be sent. Since the printer is on the same subnet, no router or default gateway is involved, so the failure lies in the ARP process—if the computer cannot obtain the printer’s MAC address, the ping will simply time out. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of when ARP is used versus DNS or DHCP; a common trap is assuming DNS is the issue when connecting by IP, but DNS only resolves names, not IP-to-MAC mappings. Remember that ARP operates at Layer 2 of the OSI model and is essential for same-subnet communication. A helpful memory tip: “Same subnet, same switch—ARP is the missing piece.”
220-1201 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 technician is troubleshooting an issue where a user's computer can access the internet but cannot connect to a network printer by its IP address. The printer is on the same subnet and is powered on. Pinging the printer's IP from the computer fails. Which network service is most likely causing the 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
✓
ARP
Since the printer is on the same subnet, no routing is needed; ARP is required to resolve the printer's IP to its MAC address. If ARP fails, the ping will fail. DNS is not used when connecting by IP, and DHCP is not involved since the computer already has an IP.
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.
✗
DNS
Why it's wrong here
The user is connecting by IP address, not hostname, so DNS is not used.
✗
DHCP
Why it's wrong here
DHCP assigns IP addresses, but the computer already has an IP and can access the internet, so DHCP is working.
✓
ARP
Why this is correct
ARP resolves the printer's IP to its MAC address. If ARP fails, the computer cannot send frames to the printer, causing ping failure.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
NAT is used for traffic between different networks; the printer is on the same subnet, so NAT is not involved.
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 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 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 Services — This question tests Network Services — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: ARP — Since the printer is on the same subnet, no routing is needed; ARP is required to resolve the printer's IP to its MAC address. If ARP fails, the ping will fail. DNS is not used when connecting by IP, and DHCP is not involved since the computer already has an IP.
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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