SK0-003 · Question #711
Which of the following ports should be allowed through a firewall for Telnet to function?
The correct answer is A. 23. Telnet uses a specific well-known port for its unencrypted communication.
Question
Which of the following ports should be allowed through a firewall for Telnet to function?
Options
- A23
- B25
- C50
- D110
How the community answered
(21 responses)- A86% (18)
- C10% (2)
- D5% (1)
Why each option
Telnet uses a specific well-known port for its unencrypted communication.
Telnet, a protocol used for remote command-line access, operates over TCP port 23. To allow Telnet communication through a firewall, inbound and/or outbound traffic on TCP port 23 must be permitted.
TCP port 25 is used by the Simple Mail Transfer Protocol (SMTP) for sending email messages.
Port 50 is not a standard well-known port for a common application protocol; it is sometimes associated with IPsec ESP.
TCP port 110 is used by the Post Office Protocol version 3 (POP3) for retrieving email messages from a server.
Concept tested: Well-known ports and services (Telnet)
Source: https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/service-overview-and-network-port-requirements
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