- A
Port 22
Why wrong: Port 22 is for SFTP, which is a different protocol over SSH.
- B
Port 20
Port 20 is the default data port for active FTP transfers.
- C
Port 23
Why wrong: Port 23 is for Telnet, not FTP.
- D
Port 69
Why wrong: Port 69 is for TFTP, a simpler file transfer protocol.
Question 659 of 1,020
FTP Data Port 20 for CompTIA A+ 220-1201
This 220-1201 practice question tests your understanding of tcp & udp ports. 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 technician is troubleshooting a legacy application that uses FTP for file transfers. The transfers work but are extremely slow. The network team mentions that the firewall is configured to inspect traffic on certain ports. Which port should be opened for FTP data transfer to improve performance?
Quick Answer
The answer is port 20, which must be opened for FTP data transfer to improve performance. FTP operates using two separate channels: port 21 handles control commands like login and directory navigation, while port 20 is dedicated to the actual data stream. When a firewall inspects or blocks port 20, the data channel becomes throttled or forced through the control channel, causing the extreme slowness described. On the CompTIA A+ Core 1 220-1201 exam, this question tests your understanding of FTP’s dual-port architecture, a common point of confusion. The trap is mixing up port 20 with port 21 (control) or port 22 (SFTP), so remember that data flows on the higher-numbered port. A useful memory tip: “Data is heavy, so it needs its own twenty.”
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
✓
Port 20
FTP uses two channels: a control channel on port 21 and a data channel on port 20 (in active mode). When a firewall inspects traffic, it may interfere with the dynamic negotiation of the data port, causing performance degradation. Opening port 20 allows the data channel to pass through without inspection, improving transfer speed.
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.
- ✗
Port 22
Why it's wrong here
Port 22 is for SFTP, which is a different protocol over SSH.
- ✓
Port 20
Why this is correct
Port 20 is the default data port for active FTP transfers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Port 23
- ✗
Port 69
Why it's wrong here
Port 69 is for TFTP, a simpler file transfer protocol.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse FTP data port 20 with the control port 21, or they mistakenly associate port 22 (SSH/SFTP) with secure file transfers, overlooking that the question specifically asks for FTP data transfer performance.
Detailed technical explanation
How to think about this question
In active FTP mode, the server initiates the data connection from port 20 to a high ephemeral port on the client. Firewalls performing deep packet inspection on the control channel (port 21) can interfere with the PORT command, causing the data connection to be blocked or delayed. Opening port 20 bypasses this inspection for the data channel, restoring performance. Passive mode (which uses random high ports) would require a different firewall configuration.
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 220-1201 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 220-1201 question test?
TCP & UDP Ports — This question tests TCP & UDP Ports — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Port 20 — FTP uses two channels: a control channel on port 21 and a data channel on port 20 (in active mode). When a firewall inspects traffic, it may interfere with the dynamic negotiation of the data port, causing performance degradation. Opening port 20 allows the data channel to pass through without inspection, improving transfer speed.
What should I do if I get this 220-1201 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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Last reviewed: Jul 4, 2026
This 220-1201 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1201 exam.
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