200-901 Network Fundamentals Practice Question
A network engineer is analyzing a packet capture of a TCP session establishment between a client and a server. The engineer observes a packet with the SYN flag set and another with both the SYN and ACK flags set. Which flag will be set in the next packet sent by the client to complete the three-way handshake?
⚠ Common exam trap
It's easy for candidates to confuse the final ACK of the three-way handshake with other TCP control flags like FIN or RST, which serve entirely different purposes in connection management.
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 three-way handshake is a fundamental TCP connection establishment process. The client sends a SYN packet, the server responds with a SYN-ACK packet, and the client completes the handshake by sending an ACK packet. This final ACK acknowledges the server's SYN and confirms that both sides are ready to exchange data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
RST
Why it's wrong here
RST is used to abruptly reset a connection, often when a packet is received that does not match any existing connection or when a port is closed. In the normal handshake process, the client does not send RST; instead, it sends an ACK to acknowledge the server's SYN-ACK and complete the connection establishment.
- ✗
PSH
Why it's wrong here
PSH is used to indicate that the receiver should pass the data to the application immediately, rather than buffering it. It is not part of the handshake process. The handshake is strictly about synchronizing sequence numbers and establishing the connection, which is accomplished with SYN, SYN-ACK, and ACK flags.
- ✗
FIN
Why it's wrong here
FIN is used to gracefully terminate an established TCP connection, not to complete the handshake. In the scenario, the connection is still being established, so sending a FIN would prematurely close the session before any data is exchanged. The client must send an ACK to finalize the handshake.
- ✓
ACK
Why this is correct
The three-way handshake consists of SYN, SYN-ACK, and ACK. The client initiates with SYN, the server responds with SYN-ACK, and the client completes the handshake by sending an ACK. This ACK acknowledges the server's SYN and establishes the connection, allowing data transfer to begin.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 200-901 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 200-901 exam.