This CV0-004 practice question tests your understanding of troubleshooting. 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.
```
$ ping 10.0.1.10
PING 10.0.1.10 (10.0.1.10) 56(84) bytes of data.
From 10.0.0.1 icmp_seq=1 Destination Host Unreachable
From 10.0.0.1 icmp_seq=2 Destination Host Unreachable
```
A cloud technician is troubleshooting connectivity from a VM with IP 10.0.0.1 to another VM at 10.0.1.10 in a different subnet. The ping output shows 'Destination Host Unreachable'. Which of the following 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The source's default gateway does not have a route to the destination network
The 'Destination Host Unreachable' error indicates that the source VM (10.0.0.1) cannot find a path to the destination subnet (10.0.1.0/24). Since the VMs are in different subnets, the source must send traffic to its default gateway. If that gateway lacks a route to 10.0.1.0/24, it will drop the packet and send an ICMP Destination Unreachable message back, causing the observed error. This is the most likely cause because the issue is at Layer 3 routing, not Layer 2 ARP or local interface problems.
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.
✗
ARP resolution for the destination IP is failing
Why it's wrong here
ARP failure would occur on the source if the destination were on the same subnet; here they are on different subnets.
✗
The network interface on the source VM is disabled
Why it's wrong here
If the NIC were disabled, the ping command would fail with a local error.
✗
A firewall is blocking ICMP on the destination
Why it's wrong here
A firewall block would cause no response or 'Request timed out', not 'Destination Host Unreachable'.
✓
The source's default gateway does not have a route to the destination network
Why this is correct
The gateway (10.0.0.1) sends 'Destination Host Unreachable' when it has no route to the destination.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between 'Destination Host Unreachable' (Layer 3 routing failure) and 'Request Timed Out' (Layer 4 or firewall blocking), tricking candidates into blaming ARP or firewalls when the real issue is a missing route on the gateway.
Trap categories for this question
Command / output trap
If the NIC were disabled, the ping command would fail with a local error.
Detailed technical explanation
How to think about this question
When a host sends a packet to a different subnet, it encapsulates the IP packet in a frame destined for its configured default gateway's MAC address via ARP. The gateway then performs a routing table lookup; if no route to the destination network exists, it sends an ICMP Type 3 Code 0 (Destination Network Unreachable) or Code 1 (Destination Host Unreachable) back to the source. In cloud environments like AWS or Azure, this often occurs when a route table associated with the source's subnet lacks a route to the destination VNet or on-premises network, or when a network virtual appliance (NVA) is misconfigured.
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 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.
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.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The source's default gateway does not have a route to the destination network — The 'Destination Host Unreachable' error indicates that the source VM (10.0.0.1) cannot find a path to the destination subnet (10.0.1.0/24). Since the VMs are in different subnets, the source must send traffic to its default gateway. If that gateway lacks a route to 10.0.1.0/24, it will drop the packet and send an ICMP Destination Unreachable message back, causing the observed error. This is the most likely cause because the issue is at Layer 3 routing, not Layer 2 ARP or local interface problems.
What should I do if I get this CV0-004 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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Question Discussion
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