N10-009 Question 84
Single answerRDP: 3389A systems administrator needs to remotely manage a Windows server at a branch office using Remote Desktop Protocol (RDP). The server is powered on and reachable over the network by IP address, and file shares on the server are accessible from the administrator's workstation. However, attempts to open a Remote Desktop session fail. A firewall review shows that only TCP ports 80, 443, and 445 are currently allowed to the server. Which change should the administrator make first to restore standard RDP connectivity?
- A
Allow TCP port 3389 from the administrator's workstation to the server
- B
Allow UDP port 53 from the administrator's workstation to the server
- C
Allow TCP port 22 from the administrator's workstation to the server
- D
Allow TCP port 445 from the server to the administrator's workstation
Show answer and explanation
Correct answer: A
Explanation
This question tests applied knowledge of common port usage in a realistic troubleshooting scenario. RDP uses TCP 3389 by default for Remote Desktop Services on Windows systems. Because the administrator can already reach the server by IP address and access file shares, basic network connectivity and SMB access are working. That makes a missing firewall rule for RDP the most likely cause. In Network+ troubleshooting, candidates should correlate the failed service with its default port rather than changing unrelated services. Microsoft documentation for Remote Desktop identifies 3389 as the default listening port for RDP, and firewall best practice is to allow only the required management traffic from authorized sources.
- A. Correct.
Correct. Standard Microsoft RDP uses TCP port 3389 by default. If the server is reachable and other services such as SMB on TCP 445 are working, but Remote Desktop connections fail, the most direct fix is to permit TCP 3389 through the firewall between the client and the server. This aligns with standard RDP deployment and troubleshooting practices.
- B. Incorrect.
Incorrect. UDP port 53 is used for DNS, not for establishing a standard RDP session. A DNS issue could affect name resolution, but the scenario states the server is reachable by IP address, which removes DNS as the primary issue.
- C. Incorrect.
Incorrect. TCP port 22 is used for SSH, which is common on Linux and network devices, but it is not the default port for Microsoft Remote Desktop. Choosing this option reflects confusion between remote administration protocols.
- D. Incorrect.
Incorrect. TCP port 445 is used for SMB/CIFS file sharing. The scenario already indicates that file shares are accessible, which strongly suggests 445 is already functioning. Opening it in the reverse direction would not address failed RDP connectivity.