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CCNA Network Infrastructure and Connectivity Practice Question
Which of the following correctly describes the sequence of the TCP three-way handshake between a client and a server?
⚠ Common exam trap
Do not confuse the roles: the client always initiates with a SYN, the server responds with SYN-ACK, and the client finishes with an ACK. Watch out for options that reverse the order or swap the flags.
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
✓
Client sends SYN, Server responds with SYN-ACK, Client sends ACK
The TCP three-way handshake establishes a reliable connection in three steps: the client sends a SYN, the server replies with SYN-ACK, and the client acknowledges with an ACK. Option A correctly depicts this. Option B omits the server's SYN, leaving synchronization incomplete. Option C reverses the roles by having the server initiate, which never occurs in a standard handshake. Option D begins with a SYN-ACK, which is not a valid initial packet; the handshake must start with a SYN.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Client sends SYN, Server responds with SYN-ACK, Client sends ACK
Why this is correct
This sequence exactly implements the TCP three-way handshake defined in RFC 793. The client first sends a SYN segment carrying its initial sequence number (ISN). The server replies with a SYN-ACK, acknowledging the client's ISN and presenting its own ISN for synchronization. The client then sends an ACK to confirm the server's ISN, after which the connection enters the ESTABLISHED state.
- ✗
Client sends SYN, Server responds with ACK, Client sends SYN-ACK
Why it's wrong here
This sequence is invalid because the server's response to a client SYN must be a SYN-ACK, not a bare ACK. Without the SYN flag, the server fails to communicate its own initial sequence number, so the two sides never achieve bidirectional sequence synchronization. Moreover, the client sending a SYN-ACK after receiving that ACK reverses the handshake roles; a SYN-ACK is a response to an initial SYN and is never generated by the client during connection setup.
- ✗
Server sends SYN, Client responds with SYN-ACK, Server sends ACK
Why it's wrong here
This option incorrectly makes the server the initiator. In TCP connection establishment, the client is the active opener and must transmit the first SYN; a server listening for connections does not initiate the handshake. If a server did send a SYN first, it would be acting as a client, which contradicts the stated relationship that the client is seeking service from the server. Additionally, once the server sends SYN, the proper response would still be SYN-ACK from the peer, not a client-side SYN-ACK, so the flag arbitration is also wrong.
- ✗
Client sends SYN-ACK, Server responds with SYN, Client sends ACK
Why it's wrong here
The client cannot send a SYN-ACK as its opening segment because the ACK flag in a SYN-ACK is meant to acknowledge a previously received SYN, and none has been sent. The correct opening segment from a client is a bare SYN with the ACK flag cleared. Placing SYN-ACK first misorders the handshake—the combined flag only makes sense as the server's reply to a client SYN, and the subsequent 'Server responds with SYN' would leave both sides in impossible states because each would be waiting for acknowledgment of their own SYN.
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 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Client sends SYN, Server responds with SYN-ACK, Client sends ACKCorrect answer▾
Why this is correct
This sequence exactly implements the TCP three-way handshake defined in RFC 793. The client first sends a SYN segment carrying its initial sequence number (ISN). The server replies with a SYN-ACK, acknowledging the client's ISN and presenting its own ISN for synchronization. The client then sends an ACK to confirm the server's ISN, after which the connection enters the ESTABLISHED state.
✗Client sends SYN, Server responds with ACK, Client sends SYN-ACKWrong answer — click to see why▾
Why this is wrong here
The server must include a SYN with its ACK to synchronize; just an ACK does not establish bidirectional sync.
Why candidates choose this
Candidates might confuse the roles, thinking the server only acknowledges the client's SYN and then the client sends a combined SYN-ACK.
✗Server sends SYN, Client responds with SYN-ACK, Server sends ACKWrong answer — click to see why▾
Why this is wrong here
The client always initiates; the server cannot start with a SYN.
Why candidates choose this
Candidates may think the handshake is symmetric or confuse it with other protocols where the server initiates.
✗Client sends SYN-ACK, Server responds with SYN, Client sends ACKWrong answer — click to see why▾
Why this is wrong here
The initial packet must be a SYN, not SYN-ACK; this sequence is out of order.
Why candidates choose this
Candidates might misremember the order or think the client sends a SYN-ACK to propose parameters.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Related to this question
Learn chapter
TCP Three-Way Handshake
Key term
TCP
TCP is a connection-oriented transport layer protocol that ensures reliable, ordered, and error-checked delivery of data between applications over IP networks.
Key term
Packet
A packet is a small unit of data that is sent over a network, containing both the actual data and control information for delivery.
About these practice questions
Courseiva writes every 200-301 question from scratch — 1,389 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco 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 200-301 exam.