What is a Command Line Interface?

A Command Line Interface (CLI) is a text-based interface used to configure and manage operating systems or network devices. Users enter text commands to perform tasks like configuring settings, managing files, or troubleshooting network issues. Unlike Graphical User Interfaces (GUIs), CLI provides direct control, faster execution, and scripting capabilities for automation. Many network devices, including managed switches, routers, and firewalls, use CLI for advanced configurations.

CLI can be accessed locally or remotely using protocols like Telnet and Secure Shell (SSH). Telnet is an older, unencrypted protocol for remote CLI access, making it insecure for modern networks. SSH is a secure alternative that encrypts communications, preventing unauthorized access and data interception. Network administrators commonly use SSH to securely access and configure devices over the network. CLI is widely used in IT, cybersecurity, and industrial automation for efficient system management and troubleshooting.

Secure Shell’s (SSH) default port is 22, and Telnet’s default port is 23. These default ports may be modified on the device hosting the CLI service. Modifying default ports may help improve security through obscurity. Network administrators should disable Telnet and use SSH to prevent security risks.

Content created by Mike Day