- A
Ping -t
Why wrong: Continuous ping may show responses if the IP is in use, but it doesn't reveal the MAC address of the responding device.
- B
arp -a
arp -a displays the ARP table, which lists IP addresses and their associated MAC addresses, helping confirm if the IP is already assigned to another device.
- C
ipconfig /all
Why wrong: ipconfig /all shows the local computer's IP configuration, not the IP usage of other devices on the network.
- D
Netstat -r
Why wrong: Netstat -r displays the routing table, which is not directly useful for checking IP address conflicts.
Question 807 of 1,020
ARP -a: Verify No Other Device Uses the Same IP
This 220-1201 practice question tests your understanding of networking tools. 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 configuring a small office network and needs to assign a static IP address to a printer. The technician pings the intended IP address and gets no reply, but the printer still fails to communicate after configuration. Which tool should be used to verify that no other device on the network is using that IP address?
Quick Answer
The answer is the `arp -a` command, because it displays the local ARP cache, which maps IP addresses to their corresponding MAC addresses. When you need to check for an IP conflict, running `arp -a` after a broadcast ping reveals whether another device’s MAC address is already cached for that IP, indicating the address is in use even if the ping got no reply. On the CompTIA A+ Core 1 220-1201 exam, this question tests your ability to troubleshoot static IP assignment failures—a common trap is assuming “no ping reply” means the IP is free, when in fact a silent device or a cached entry from a prior response can cause a conflict. The key insight is that `arp` works at Layer 2, so it catches conflicts that ICMP might miss. Memory tip: think “ARP-a for ARP cache, IP-MAC match to avoid a clash.”
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
✓
arp -a
The `arp -a` command displays the current ARP cache, which maps IP addresses to MAC addresses on the local network. If another device is already using the intended IP address, its MAC address will appear in the ARP cache for that IP, confirming a conflict. This is the correct tool because it directly shows which MAC address is associated with the IP, even if the device does not respond to ping (e.g., due to firewall rules).
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.
- ✗
Ping -t
Why it's wrong here
Continuous ping may show responses if the IP is in use, but it doesn't reveal the MAC address of the responding device.
- ✓
arp -a
Why this is correct
arp -a displays the ARP table, which lists IP addresses and their associated MAC addresses, helping confirm if the IP is already assigned to another device.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
ipconfig /all
Why it's wrong here
ipconfig /all shows the local computer's IP configuration, not the IP usage of other devices on the network.
- ✗
Netstat -r
Why it's wrong here
Netstat -r displays the routing table, which is not directly useful for checking IP address conflicts.
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common misconception is that a successful ping (or lack of reply) is sufficient to verify IP availability, when in fact ARP is the definitive tool to detect IP conflicts because it works even when ICMP is blocked.
Trap categories for this question
Command / output trap
Continuous ping may show responses if the IP is in use, but it doesn't reveal the MAC address of the responding device.
Detailed technical explanation
How to think about this question
The ARP protocol operates at Layer 2 (Data Link) and Layer 3 (Network) of the OSI model, maintaining a cache of recently resolved IP-to-MAC mappings. When a device sends an ARP request for an IP that is already in use, the existing owner replies with its MAC address, populating the cache; `arp -a` reads this cache. In real-world scenarios, a silent IP conflict can occur when a device has a static IP that overlaps with a DHCP lease, and the DHCP server may not respond to pings, but the ARP cache will still show the conflicting MAC.
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 practitioner preparing for the 220-1201 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.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Networking Tools — This question tests Networking Tools — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: arp -a — The `arp -a` command displays the current ARP cache, which maps IP addresses to MAC addresses on the local network. If another device is already using the intended IP address, its MAC address will appear in the ARP cache for that IP, confirming a conflict. This is the correct tool because it directly shows which MAC address is associated with the IP, even if the device does not respond to ping (e.g., due to firewall rules).
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.
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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