Basics of IT Infrastructure and IT Project Management →easyMultiple ChoiceObjective-mapped

PK0-005 Practice Question: Basics of IT Infrastructure and IT Project Management

Exhibit

Refer to the exhibit.

Exhibit:
```
2023-09-15 14:23:45 ERROR [main] com.example.app.DatabaseConnection - Connection refused: connect
2023-09-15 14:23:46 WARN  [main] com.example.app.DatabaseConnection - Retrying connection...
2023-09-15 14:23:50 ERROR [main] com.example.app.DatabaseConnection - Connection refused: connect
2023-09-15 14:23:51 FATAL [main] com.example.app.Application - Unable to start application due to database failure
```

A project team is deploying a new application, and the error log shows repeated connection refused errors. The database server is on a separate subnet. What is the most likely cause of this issue?

⚠ Common exam trap

Candidates may misinterpret 'connection refused' as an authentication issue or schema error, but in a scenario where servers are on different subnets, a firewall blocking the port is the most likely cause. This tests the ability to distinguish network-layer errors from application-layer errors in a project environment.

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 database port is blocked by a firewall

The error 'connection refused' indicates that the application's TCP SYN packet to the database server was met with a TCP RST or no response, which typically occurs when a firewall drops or rejects the traffic. Since the database server is on a separate subnet, a network-layer access control list (ACL) or firewall rule is the most common cause of blocking the specific database port (e.g., 3306 for MySQL, 5432 for PostgreSQL, 1433 for SQL Server). This prevents the three-way handshake from completing, resulting in the connection refused error.

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 database port is blocked by a firewall
Why this is correct
Firewall blocking the port results in connection refused errors.
✗
The database schema is missing a required table
Why it's wrong here
Missing tables cause SQL errors, not connection refused.
✗
The database credentials are incorrect
Why it's wrong here
Incorrect credentials would produce authentication errors, not connection refused.
✗
The application server has insufficient memory
Why it's wrong here
Memory issues would cause crashes or slowness, not connection refused.

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PK0-005 Practice Question: Basics of IT Infrastructure and IT Project Management

Exhibit

Why each option matters

Option-by-option breakdown

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