This CV0-004 practice question tests your understanding of operations and support. 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 cloud administrator is troubleshooting an application that fails to connect to a database. The application and database are in the same VPC. Which THREE steps should the administrator take to diagnose the issue?
Check the routing table for a route to the internet.
Why wrong: No internet access needed for internal communication.
B
Test connectivity to the database using a telnet or netcat command from the application server.
Direct connectivity test isolates the issue.
C
Verify that the security group associated with the database instance allows inbound traffic from the application's security group on the database port.
Security groups control traffic to the database.
D
Check the DNS resolution of the database endpoint in the application's subnet.
Why wrong: DNS is unlikely to be the issue in same VPC.
E
Verify that the network ACL for the database subnet allows inbound traffic on the database port.
Network ACLs are stateless and must allow traffic.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Test connectivity to the database using a telnet or netcat command from the application server.
Option B is correct because telnet or netcat can test basic TCP connectivity to the database port, confirming whether the database is reachable from the application server at the network layer. This step isolates whether the issue is a network connectivity problem versus an authentication or configuration issue within the database itself.
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.
✗
Check the routing table for a route to the internet.
Why it's wrong here
No internet access needed for internal communication.
✓
Test connectivity to the database using a telnet or netcat command from the application server.
Why this is correct
Direct connectivity test isolates the issue.
Related concept
Read the scenario before looking for a memorised answer.
✓
Verify that the security group associated with the database instance allows inbound traffic from the application's security group on the database port.
Why this is correct
Security groups control traffic to the database.
Related concept
Read the scenario before looking for a memorised answer.
✗
Check the DNS resolution of the database endpoint in the application's subnet.
Verify that the network ACL for the database subnet allows inbound traffic on the database port.
Why this is correct
Network ACLs are stateless and must allow traffic.
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 stateful security groups and stateless network ACLs, and candidates mistakenly assume that allowing inbound traffic in the security group alone is sufficient, forgetting that network ACLs must also permit the traffic.
Detailed technical explanation
How to think about this question
When troubleshooting connectivity within a VPC, the order of checks typically follows the OSI model: first verify network ACLs (stateless, Layer 3/4), then security groups (stateful, Layer 4), and finally application-layer connectivity using tools like telnet or netcat. A common subtlety is that security groups are stateful, so outbound return traffic is automatically allowed, whereas network ACLs require explicit inbound and outbound rules; misconfigured ACLs can cause asymmetric traffic drops that appear as timeouts.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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.
Operations and Support — This question tests Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Test connectivity to the database using a telnet or netcat command from the application server. — Option B is correct because telnet or netcat can test basic TCP connectivity to the database port, confirming whether the database is reachable from the application server at the network layer. This step isolates whether the issue is a network connectivity problem versus an authentication or configuration issue within the database itself.
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.
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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