N10-009 Question 82
Single answerSQL Server: 1433A company migrates its customer database to a new Microsoft SQL Server hosted in a secure data center. After the move, the application servers in another subnet can reach the server with ICMP ping, but the application cannot connect to the database. A network administrator reviews the path and sees no routing issues. The database team confirms the SQL Server instance is configured to accept remote connections using its default port. Which firewall change is the MOST likely required to restore application connectivity?
- A
Allow inbound TCP 1433 to the SQL Server from the application server subnet
- B
Allow inbound UDP 1433 to the SQL Server from the application server subnet
- C
Allow inbound TCP 3389 to the SQL Server from the application server subnet
- D
Allow inbound UDP 53 to the SQL Server from the application server subnet
Show answer and explanation
Correct answer: A
Explanation
This scenario tests practical port and protocol knowledge in a troubleshooting context. Microsoft SQL Server commonly uses TCP port 1433 for client connections to the database engine on the default port. If ICMP works and routing is intact, but the application still cannot connect, a blocked service port at the firewall is a likely cause. The best corrective action is to allow inbound TCP 1433 from the authorized application server subnet to the SQL Server. This aligns with Microsoft's SQL Server network configuration guidance, which identifies TCP 1433 as the standard listener for SQL Server client connectivity when configured on the default port. From a Network+ perspective, the key skill is mapping the application service to the correct transport protocol and port, then applying the least-privilege firewall rule needed for the business function.
- A. Correct.
Correct. Microsoft SQL Server commonly listens on TCP port 1433 for client connections when using the default instance or when configured for the default SQL Server port. If the application servers can reach the host at Layer 3 but cannot establish a database session, permitting inbound TCP 1433 from the application subnet is the most likely required firewall rule.
- B. Incorrect.
Incorrect. SQL Server client connections do not normally use UDP 1433. A common misconception is to match the port number but ignore the transport protocol. SQL Server database traffic for standard client sessions uses TCP 1433, not UDP 1433.
- C. Incorrect.
Incorrect. TCP 3389 is used for Remote Desktop Protocol (RDP), which would allow administrative remote desktop access to the server, not SQL database connectivity for applications. This distractor targets confusion between server management access and application service access.
- D. Incorrect.
Incorrect. UDP 53 is used for DNS queries and responses. DNS may be necessary for name resolution in some environments, but if the issue is specifically application access to a SQL Server confirmed to be listening on its default port, opening UDP 53 to the SQL Server would not resolve the database connectivity problem.