Which port/service matches TCP port 21?

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Prepare for the Certified Ethical Hacker Version 11 Exam with a comprehensive test featuring flashcards and multiple choice questions, each accompanied by hints and explanations to ensure a thorough understanding. Ace your ethical hacking exam with confidence!

Multiple Choice

Which port/service matches TCP port 21?

Explanation:
Understanding standard port-to-service mappings helps you interpret network traffic. TCP port 21 is the control channel for FTP, where commands like USER, PASS, and LIST are exchanged to manage the session. The actual file transfers use a separate data channel, typically on port 20 in active FTP, or on dynamically assigned ports in passive FTP. For reference, SSH uses port 22 and DNS uses port 53, while FTP data uses port 20. So the service matching TCP port 21 is the FTP control channel.

Understanding standard port-to-service mappings helps you interpret network traffic. TCP port 21 is the control channel for FTP, where commands like USER, PASS, and LIST are exchanged to manage the session. The actual file transfers use a separate data channel, typically on port 20 in active FTP, or on dynamically assigned ports in passive FTP. For reference, SSH uses port 22 and DNS uses port 53, while FTP data uses port 20. So the service matching TCP port 21 is the FTP control channel.

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