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Question

Difficulty: EasyCommon Ports and Protocols

A systems administrator is configuring a host-based firewall on a Linux management server. The server must accept incoming secure remote command-line administration sessions using Secure Shell (SSH). Which of the following port and transport protocol combinations must be permitted?

  1. TCP port 22Answer
  2. B
    UDP port 22
  3. C
    TCP port 23
  4. D
    UDP port 23

Answer

TCP port 22
Secure Shell (SSH) is a secure, encrypted protocol for remote terminal connections that operates by default over TCP port 22.

Step-by-Step Solution

1
Identify the service protocol requested
The scenario specifies Secure Shell (SSH) for secure command-line administration.
Determining the target protocol establishes the baseline default port number requirement.
2
Determine the default port number for SSH
SSH defaults to port 22.
Standard well-known port allocations assign port 22 to SSH and port 23 to Telnet.
3
Determine the transport layer protocol requirement
SSH uses TCP.
Interactive management sessions require reliable, connection-oriented data transfer provided by TCP.

Key Concept

Default Port and Transport Protocol for SSH
Estimated Time:45s
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Topics

Common Ports and Protocols

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