TCP is a connection-oriented protocol that guarantees ordered, reliable delivery, while UDP is faster but does not guarantee delivery. Knowing when each is used helps you understand and troubleshoot network services.

DNS (Domain Name System) translates human-readable names such as example.com into the IP addresses computers use to connect. Diagnosing DNS resolution is a common and essential administration task covered in the course.

A port is a numbered endpoint that identifies a specific service on a system, allowing one machine to run many network services at once. Mapping services to ports is central to both configuration and security.

tcpdump is a command-line tool that captures and displays network traffic in real time. Administrators use it to inspect packets, diagnose problems, and understand activity on a network.

SSH (Secure Shell) is the standard protocol for securely accessing and managing a Linux system over a network. The course covers key-based authentication, secure file transfer, and hardening SSH against attacks.

Key-based authentication uses a cryptographic key pair instead of a password to verify identity over SSH. It is more secure than passwords and is standard practice for protecting remote access.

A firewall controls which network traffic is allowed in and out of a system based on configured rules. Configuring one correctly is a core defense against unauthorized access.

nmap is a network scanning tool that discovers hosts and identifies open ports and services. Administrators use it to audit their own systems and find exposed services that need securing.

Fail2ban is an intrusion prevention tool that monitors logs for repeated failed login attempts and automatically blocks the sources. It helps protect services such as SSH from brute-force attacks.

You should be comfortable at the Linux command line before starting. The networking and security tools here run from the terminal, so the earlier courses provide the right foundation.

Yes. It is the final course in the Linux System Administration Specialization and brings together command-line, administration, and scripting skills. It can also be taken on its own.

Yes. You earn a shareable Course Certificate on completion, which you can add to a resume and LinkedIn profile.

To access the course materials, assignments and to earn a Certificate, you will need to purchase the Certificate experience when you enroll in a course. You can try a Free Trial instead, or apply for Financial Aid. The course may offer 'Full Course, No Certificate' instead. This option lets you see all course materials, submit required assessments, and get a final grade. This also means that you will not be able to purchase a Certificate experience.

When you enroll in the course, you get access to all of the courses in the Specialization, and you earn a certificate when you complete the work. Your electronic Certificate will be added to your Accomplishments page - from there, you can print your Certificate or add it to your LinkedIn profile.