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CCNA Network Infrastructure and Connectivity Practice Question
Drag and drop the following steps into the correct order to sequence the TCP three-way handshake between a client and a server.
⚠ Common exam trap
A common trap is confusing the order of the handshake or thinking the server initiates the connection. Remember: the client always sends the first SYN, and the server's response is a SYN-ACK (not a separate SYN and ACK).
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
The TCP three-way handshake starts with the client sending a SYN, followed by the server responding with SYN-ACK, and finally the client sending an ACK to establish the connection.
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
Why this is correct
The client initiates the TCP three-way handshake by sending a segment with the SYN flag set and a randomly generated initial sequence number (ISN). This SYN carries no application payload and tells the server that the client wants to synchronize sequence numbers and establish a connection; the client then transitions from CLOSED to SYN-SENT state.
- ✓
Server sends SYN-ACK
Why this is correct
The server receives the client's SYN and replies with a segment that sets both the SYN and ACK flags, known as SYN-ACK. In this packet, the server acknowledges the client's ISN by placing ISN+1 in the acknowledgment field, and simultaneously sends its own ISN. This step proves the server received the client's SYN and is willing to establish a bidirectional connection, placing the server in SYN-RECEIVED state.
- ✓
Client sends ACK
Why this is correct
After receiving the SYN-ACK, the client sends a final segment with the ACK flag set, carrying an acknowledgment number equal to the server's ISN+1. This packet does not have the SYN flag, and it confirms that both sides have successfully synchronized sequence numbers. Upon receiving this ACK, the server moves to ESTABLISHED state, and the connection is fully open for data transfer.
- ✗
Server sends ACK
Why it's wrong here
A standalone ACK sent by the server is not a valid step in the TCP three-way handshake. During the handshake, the server's only ACK-carrying segment is the SYN-ACK, which combines the acknowledgment of the client's SYN with the server's own SYN flag. If the server were to send a pure ACK without the SYN flag at the beginning, it would not be part of the handshake and would likely indicate an unsolicited or out-of-state packet, which could be a spoofing or error condition.
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 SYNCorrect answer▾
Why this is correct
The client initiates the TCP three-way handshake by sending a segment with the SYN flag set and a randomly generated initial sequence number (ISN). This SYN carries no application payload and tells the server that the client wants to synchronize sequence numbers and establish a connection; the client then transitions from CLOSED to SYN-SENT state.
✗Server sends ACKWrong answer — click to see why▾
Why this is wrong here
In a normal three-way handshake, the server does not send a separate ACK after the client's ACK; the connection is already established.
Why candidates choose this
Candidates might think the server sends an ACK separately, but in the three-way handshake, the server's acknowledgment is piggybacked with its own SYN.
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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TCP Three-Way Handshake
Key term
TCP
TCP (Transmission Control Protocol) is a core internet protocol that ensures data is sent reliably and in order between devices over a network.
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.
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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.