- A
ACK
The final acknowledgment (ACK) confirms the server's SYN-ACK and completes the handshake.
- B
RST
Why wrong: RST is used to reset a connection, not to complete the handshake.
- C
FIN
Why wrong: FIN is used to gracefully close a connection, not to establish it.
- D
SYN
Why wrong: A second SYN would indicate a new attempt, not a continuation of the handshake.
Question 260 of 520
N10-009 Networking Concepts Practice Question
This N10-009 practice question tests your understanding of networking concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 client and server are establishing a TCP connection. The client sends a SYN segment to the server. The server responds with a SYN-ACK segment. What is the next segment in the handshake?
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
✓
ACK
The TCP three-way handshake requires the client to acknowledge the server's SYN-ACK by sending an ACK segment. This completes the handshake, establishing a full-duplex connection with synchronized sequence numbers. Without this final ACK, the server remains in a half-open state, unable to begin data transmission.
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.
- ✓
ACK
Why this is correct
The final acknowledgment (ACK) confirms the server's SYN-ACK and completes the handshake.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
RST
Why it's wrong here
RST is used to reset a connection, not to complete the handshake.
When this WOULD be correct
A question asks: 'After a client sends a SYN to a closed port, the server responds with an RST. What is the next segment?' In that case, the server sends RST, not SYN-ACK, and the client does not send anything further.
- ✗
FIN
Why it's wrong here
FIN is used to gracefully close a connection, not to establish it.
When this WOULD be correct
In a question about TCP connection termination, after the server sends a FIN segment, the client would respond with an ACK (or the server might send FIN after receiving a FIN from the client).
- ✗
SYN
Why it's wrong here
A second SYN would indicate a new attempt, not a continuation of the handshake.
When this WOULD be correct
A question asking about the first step of the TCP handshake: 'What does a client send to initiate a connection?' would have SYN as the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓ACKCorrect answer▾
Why this is correct
The final acknowledgment (ACK) confirms the server's SYN-ACK and completes the handshake.
✗RSTWrong answer — click to see why▾
Why this is wrong here
In a TCP three-way handshake, after the server sends SYN-ACK, the client must send an ACK to complete the connection. RST is used to reset a connection, not to continue the handshake.
★ When this WOULD be the correct answer
A question asks: 'After a client sends a SYN to a closed port, the server responds with an RST. What is the next segment?' In that case, the server sends RST, not SYN-ACK, and the client does not send anything further.
Why candidates choose this
Candidates may confuse RST with ACK or think that a reset is part of the normal handshake, especially if they recall that RST can be used to reject a connection attempt.
✗FINWrong answer — click to see why▾
Why this is wrong here
The TCP three-way handshake requires an ACK from the client after receiving SYN-ACK; FIN is used to terminate a connection, not to establish it.
★ When this WOULD be the correct answer
In a question about TCP connection termination, after the server sends a FIN segment, the client would respond with an ACK (or the server might send FIN after receiving a FIN from the client).
Why candidates choose this
Candidates may confuse the connection establishment handshake with the termination handshake, where FIN is a key segment.
✗SYNWrong answer — click to see why▾
Why this is wrong here
In the TCP three-way handshake, after the server sends SYN-ACK, the client must send an ACK to complete the connection. Sending a SYN again would be redundant and violate the handshake sequence.
★ When this WOULD be the correct answer
A question asking about the first step of the TCP handshake: 'What does a client send to initiate a connection?' would have SYN as the correct answer.
Why candidates choose this
Candidates may confuse the handshake steps or think that the client needs to send another SYN to confirm, not realizing that the SYN-ACK already acknowledges the client's SYN.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The N10-009 exam often tests the misconception that the handshake ends after the SYN-ACK, or that a FIN or RST could be used to complete the handshake, when in fact the final ACK is mandatory to transition the server's state from SYN-RECEIVED to ESTABLISHED.
Detailed technical explanation
How to think about this question
During the TCP three-way handshake, the client's initial SYN carries an Initial Sequence Number (ISN), and the server's SYN-ACK acknowledges that ISN (by sending ACK = client_ISN + 1) while providing its own ISN. The final ACK from the client acknowledges the server's ISN (ACK = server_ISN + 1), and this segment may already contain payload data (as per RFC 1122). In real-world scenarios, this final ACK can be piggybacked with the first application data, reducing latency in protocols like HTTP.
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 N10-009 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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ACK — The TCP three-way handshake requires the client to acknowledge the server's SYN-ACK by sending an ACK segment. This completes the handshake, establishing a full-duplex connection with synchronized sequence numbers. Without this final ACK, the server remains in a half-open state, unable to begin data transmission.
What should I do if I get this N10-009 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: Jun 11, 2026
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