Which of the following protocol ports is used for secure remote access to a network...

Port 22 is used by SSH (Secure Shell), which is the standard protocol for secure remote administration of network devices such as switches, routers, firewalls, and Linux-based systems. CompTIA A+ Core 1 emphasizes knowing common ports and selecting secure management methods. SSH provides encrypted communication for both authentication and the session data, protecting usernames, passwords, and command output from being intercepted by packet sniffers. This makes it the preferred choice over older remote access methods.

In contrast, port 23 is Telnet, which is also used for remote terminal access but sends traffic in cleartext, making it insecure and generally discouraged in modern environments. Port 21 is FTP control traffic, used for file transfers and typically not secure unless paired with FTPS or replaced by SFTP (which actually runs over SSH on port 22). Port 25 is SMTP, used for sending email between mail servers and is unrelated to remote device management. Therefore, for secure remote access to a network device, SSH on port 22 is the correct answer.