Telnet commonly uses port 23 for its operations. This is crucial for network technicians to know because while configuring firewalls and network policies, distinguishing between ports used by different services ensures proper traffic flow and security measures. Port 22 is used by SSH, which is a secure alternative to Telnet. Ports 21, 25, and 80 are typically used by FTP, SMTP, and HTTP, respectively, which serve different functions.