A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass. wikipedia.org

Network security consists of the provisions and policies adopted by the network administrator to prevent and monitor unauthorized access, misuse, modification, or denial of the computer network and network-accessible resources. wikipedia.org

A network administrator, network analyst or network engineer is a person responsible for the maintenance of computer hardware and software that comprises a computer network. This normally includes deploying, configuring, maintaining and monitoring active network equipment. wikipedia.org

"The CCNP is the credential that validates the ability to work with medium-sized networks (between 100 and 500 end devices) and with technology such as QoS, broadband, VPNs, and security-minded features."

Windows Server is a brand name for a group of server operating systems released by Microsoft. wikipedia.org

A system administrator, or sysadmin, is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems; especially multi-user computers, such as servers. wikipedia.org

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. wikipedia.org

Cisco Certified Network Associate (CCNA) Routing and Switching is a certification program for entry-level network engineers that helps maximize your investment in foundational networking knowledge.

pfSense is an open source firewall/router distribution based on FreeBSD. pfSense is meant to be installed on a personal computer and is noted for its reliability and offering features often only found in expensive commercial firewalls. wikipedia.org

Ubiquiti manufactures wireless data communication products for enterprise and wireless broadband providers.

A virtual private network (VPN) is a network that uses primarily public telecommunication infrastructure, such as the Internet, to provide remote offices or traveling users access to a central organizational network. wikipedia.org