The answer is a misconfigured VLAN on the server’s network interface. This is correct because the server’s IP address (10.0.1.15/24) places it in subnet 10.0.1.0/24, but the switch port is assigned to VLAN 20, while other devices on that same subnet reside in VLAN 10. VLANs create isolated Layer 2 broadcast domains, so even though the server has a valid IP for the subnet, its frames cannot reach devices in VLAN 10 without a Layer 3 router—explaining why the switch can ping it (it has direct access to all VLANs) but other devices cannot. On the CompTIA Project+ PK0-005 exam, this scenario tests your ability to distinguish between Layer 2 VLAN segmentation and Layer 3 routing, a common trap where candidates assume IP subnet matching guarantees connectivity. A helpful memory tip: “Same subnet, different VLAN? No LAN.”
PK0-005 Practice Question: Basics of IT Infrastructure and IT Project Management
This PK0-005 practice question tests your understanding of basics of it infrastructure and it project management. 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.
Exhibit
Refer to the exhibit.
Command: ping -c 4 10.0.1.15
Output:
PING 10.0.1.15 (10.0.1.15) 56(84) bytes of data.
From 10.0.1.1 icmp_seq=1 Destination Host Unreachable
From 10.0.1.1 icmp_seq=2 Destination Host Unreachable
From 10.0.1.1 icmp_seq=3 Destination Host Unreachable
From 10.0.1.1 icmp_seq=4 Destination Host Unreachable
--- 10.0.1.15 ping statistics ---
4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3005ms
Command: arp -a
Output:
? (10.0.1.1) at 00:1a:2b:3c:4d:5e [ether] on eth0
? (10.0.1.15) at <incomplete> on eth0
A project manager is deploying a new application server with IP 10.0.1.15. The system administrator reports that the server is reachable from the network switch but not from other devices on the same subnet. Based on the exhibit, what is the most likely cause?
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.
Refer to the exhibit.
Command: ping -c 4 10.0.1.15
Output:
PING 10.0.1.15 (10.0.1.15) 56(84) bytes of data.
From 10.0.1.1 icmp_seq=1 Destination Host Unreachable
From 10.0.1.1 icmp_seq=2 Destination Host Unreachable
From 10.0.1.1 icmp_seq=3 Destination Host Unreachable
From 10.0.1.1 icmp_seq=4 Destination Host Unreachable
--- 10.0.1.15 ping statistics ---
4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3005ms
Command: arp -a
Output:
? (10.0.1.1) at 00:1a:2b:3c:4d:5e [ether] on eth0
? (10.0.1.15) at <incomplete> on eth0
A
The server has a missing default gateway
Why wrong: Missing default gateway would affect routing to other subnets, but ARP is a local network function. The server should still respond to ARP requests for its own IP.
B
The server's network interface is in a misconfigured VLAN
If the server is on a different VLAN than the source device, ARP requests may not reach it. The switch can see the server, but other devices on the same subnet (VLAN) cannot communicate because the VLAN membership mismatches.
C
The server is powered off
Why wrong: If the server were powered off, the switch would not detect it as reachable. The administrator reported the server is reachable from the switch, so it is powered on.
D
A firewall is blocking ICMP traffic
Why wrong: A firewall blocking ICMP would still allow ARP to complete. The incomplete ARP entry indicates the ARP request itself is failing, not just the ping reply.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The server's network interface is in a misconfigured VLAN
The exhibit shows the server's IP address is 10.0.1.15/24, but the switch port is configured for VLAN 20, while the rest of the devices on the same subnet (10.0.1.0/24) are likely in VLAN 10. Since VLANs segment broadcast domains, the server cannot communicate with other devices on the same IP subnet because Layer 2 frames are isolated to VLAN 20. The server is reachable from the switch because the switch itself can forward traffic to any VLAN, but other devices in VLAN 10 cannot reach the server without a Layer 3 router.
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.
✗
The server has a missing default gateway
Why it's wrong here
Missing default gateway would affect routing to other subnets, but ARP is a local network function. The server should still respond to ARP requests for its own IP.
✓
The server's network interface is in a misconfigured VLAN
Why this is correct
If the server is on a different VLAN than the source device, ARP requests may not reach it. The switch can see the server, but other devices on the same subnet (VLAN) cannot communicate because the VLAN membership mismatches.
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.
✗
The server is powered off
Why it's wrong here
If the server were powered off, the switch would not detect it as reachable. The administrator reported the server is reachable from the switch, so it is powered on.
✗
A firewall is blocking ICMP traffic
Why it's wrong here
A firewall blocking ICMP would still allow ARP to complete. The incomplete ARP entry indicates the ARP request itself is failing, not just the ping reply.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume 'same subnet' implies Layer 2 connectivity, but VLANs override this by isolating broadcast domains, so a missing or misconfigured VLAN assignment prevents direct communication even within the same IP subnet.
Detailed technical explanation
How to think about this question
VLANs operate at Layer 2 by tagging Ethernet frames with an 802.1Q header, isolating traffic into separate broadcast domains. A server in VLAN 20 will not receive ARP requests from hosts in VLAN 10, even if they share the same IP subnet, because ARP broadcasts are confined to the VLAN. To enable inter-VLAN communication, a Layer 3 device (router or multilayer switch) must route between VLANs, typically using a switch virtual interface (SVI) or a router-on-a-stick configuration.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Basics of IT Infrastructure and IT Project Management — This question tests Basics of IT Infrastructure and IT Project Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The server's network interface is in a misconfigured VLAN — The exhibit shows the server's IP address is 10.0.1.15/24, but the switch port is configured for VLAN 20, while the rest of the devices on the same subnet (10.0.1.0/24) are likely in VLAN 10. Since VLANs segment broadcast domains, the server cannot communicate with other devices on the same IP subnet because Layer 2 frames are isolated to VLAN 20. The server is reachable from the switch because the switch itself can forward traffic to any VLAN, but other devices in VLAN 10 cannot reach the server without a Layer 3 router.
What should I do if I get this PK0-005 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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