- A
The EC2 instance has exhausted its CPU credits, causing the application to become unresponsive.
Why wrong: CPU exhaustion would not produce a SQL login error; the application would likely report timeouts or latency, not a specific login failure.
- B
The Azure SQL Database firewall does not allow traffic from the EC2 instance's IP address or the VPN gateway's IP.
Azure SQL has a firewall that must explicitly permit the source IP. The error 'login failed' often indicates the IP is blocked. The admin should add the VPN gateway's public IP to the allowed list.
- C
The VPN tunnel is not properly routing traffic to Azure, causing intermittent connectivity.
Why wrong: The VPN status is UP, and the issue is a login failure, not a connectivity failure. Routing would show as unreachable, not a login error.
- D
The EC2 instance does not have sufficient IAM permissions to connect to Azure SQL Database.
Why wrong: IAM permissions apply to AWS resources, not Azure. Azure SQL uses SQL authentication or Azure AD, not AWS IAM.
Quick Answer
The answer is that the Azure SQL Database firewall does not allow traffic from the EC2 instance's IP address or the VPN gateway's IP. This is correct because Azure SQL Database enforces server-level firewall rules that explicitly whitelist source IP addresses; without a rule permitting the traffic routed through the site-to-site VPN, the database rejects the connection with the login-failed error, even though the VPN tunnel shows as UP and the EC2 instance passes health checks. On the CompTIA Cloud+ CV0-004 exam, this scenario tests your understanding of multi-cloud database connectivity and how Azure SQL firewall rules differ from network-level security groups—a common trap is assuming a healthy VPN alone guarantees database access. Remember, Azure SQL’s firewall is IP-based, not tunnel-aware, so you must add either the EC2 instance’s private IP (if traffic traverses the VPN) or the VPN gateway’s public IP to the firewall allow list. Memory tip: “VPN up, SQL blocked? Check the firewall’s IP docked.”
CV0-004 Troubleshooting Practice Question
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.
A company uses a multi-cloud strategy with workloads on AWS and Azure. An application running on an Amazon EC2 instance in a VPC uses an Azure SQL Database as its backend via a site-to-site VPN. Recently, users reported intermittent timeouts when accessing the application. The EC2 instance passes health checks, and the VPN tunnel status shows as 'UP' from both sides. The application logs show 'Cannot open server 'azuresql.database.windows.net' requested by the login. The login failed.' Which of the following is the MOST likely cause of the issue?
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 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
The Azure SQL Database firewall does not allow traffic from the EC2 instance's IP address or the VPN gateway's IP.
The error message 'Cannot open server 'azuresql.database.windows.net' requested by the login. The login failed.' indicates that the Azure SQL Database server rejected the connection attempt. Since the VPN tunnel is 'UP' and the EC2 instance passes health checks, the most likely cause is that the Azure SQL Database firewall rules do not include the source IP address of the traffic coming from the EC2 instance — either the EC2 instance's private IP (if traffic is routed through the VPN) or the public IP of the VPN gateway. Azure SQL Database uses server-level firewall rules to allow client IP addresses, and without an explicit rule, all connections are blocked.
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 EC2 instance has exhausted its CPU credits, causing the application to become unresponsive.
Why it's wrong here
CPU exhaustion would not produce a SQL login error; the application would likely report timeouts or latency, not a specific login failure.
- ✓
The Azure SQL Database firewall does not allow traffic from the EC2 instance's IP address or the VPN gateway's IP.
Why this is correct
Azure SQL has a firewall that must explicitly permit the source IP. The error 'login failed' often indicates the IP is blocked. The admin should add the VPN gateway's public IP to the allowed list.
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 VPN tunnel is not properly routing traffic to Azure, causing intermittent connectivity.
Why it's wrong here
The VPN status is UP, and the issue is a login failure, not a connectivity failure. Routing would show as unreachable, not a login error.
- ✗
The EC2 instance does not have sufficient IAM permissions to connect to Azure SQL Database.
Why it's wrong here
IAM permissions apply to AWS resources, not Azure. Azure SQL uses SQL authentication or Azure AD, not AWS IAM.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates see a VPN tunnel status of 'UP' and assume connectivity is fully functional, overlooking that Azure SQL Database has its own separate firewall layer that must explicitly permit the source IP address of the connecting client.
Trap categories for this question
Command / output trap
The VPN status is UP, and the issue is a login failure, not a connectivity failure. Routing would show as unreachable, not a login error.
Detailed technical explanation
How to think about this question
Azure SQL Database firewall rules operate at the server level and can be configured to allow specific client IP addresses or Azure service IP ranges. When traffic traverses a site-to-site VPN, the source IP seen by Azure SQL is typically the private IP of the EC2 instance (if the VPN is routed through the VPC) or the public IP of the Azure VPN gateway. The error 'Cannot open server... requested by the login' is a specific SQL Server error (error 4060) that occurs when the client IP is not allowed by the firewall, even if the VPN tunnel is healthy. In a multi-cloud setup, administrators often forget to add the on-premises or cloud VPN gateway's public IP to the Azure SQL firewall allow list.
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 CV0-004 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.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this CV0-004 question test?
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 Azure SQL Database firewall does not allow traffic from the EC2 instance's IP address or the VPN gateway's IP. — The error message 'Cannot open server 'azuresql.database.windows.net' requested by the login. The login failed.' indicates that the Azure SQL Database server rejected the connection attempt. Since the VPN tunnel is 'UP' and the EC2 instance passes health checks, the most likely cause is that the Azure SQL Database firewall rules do not include the source IP address of the traffic coming from the EC2 instance — either the EC2 instance's private IP (if traffic is routed through the VPN) or the public IP of the VPN gateway. Azure SQL Database uses server-level firewall rules to allow client IP addresses, and without an explicit rule, all connections are blocked.
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.
About these practice questions
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Last reviewed: Jun 25, 2026
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