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Difficulty: MediumCommon Ports and Protocols

During a routine internal security audit, a network analyst discovers that administrators are using Telnet to remotely configure network infrastructure devices, exposing authentication credentials in unencrypted cleartext across internal subnets. Security policy requires immediately replacing this practice with Secure Shell (SSH) to secure all interactive administrative sessions. Which default port and transport layer protocol combination must be permitted on internal firewalls to allow SSH traffic?

  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) operates over TCP port 22 by default. SSH provides encrypted terminal management sessions and relies on TCP's connection-oriented delivery to maintain session integrity.

Step-by-Step Solution

1
Identify the target secure administration protocol.
The scenario requires implementing Secure Shell (SSH) to replace unencrypted Telnet sessions.
SSH encrypts management traffic, preserving confidentiality for administrative credentials and commands.
2
Determine the transport layer protocol required by SSH.
SSH requires Transmission Control Protocol (TCP) to ensure reliable, connection-oriented data delivery.
Interactive shell sessions depend on ordered delivery and error recovery provided by TCP.
3
Identify the standard IANA assigned port for SSH.
SSH operates on default port 22.
Standard network firewall rules reference IANA default port allocations for service filtering.

Key Concept

Common Ports and Protocols - SSH (TCP 22) vs Telnet (TCP 23)
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Topics

Common Ports and Protocols

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