A firewall is a network security device or software that monitors and controls incoming and outgoing network traffic based on predefined security rules. Acting as a barrier between trusted internal networks (e.g., a corporate LAN) and untrusted external networks (e.g., the internet), firewalls prevent unauthorized access, block malicious traffic, and protect sensitive data. They are a cornerstone of modern cybersecurity strategies.

Network routing is the process of selecting optimal paths for data packets to travel across interconnected networks, ensuring they reach their intended destinations. Routers, which operate at the Network Layer (Layer 3) of the OSI model, use routing protocols and algorithms to direct traffic between different networks, such as LANs, WANs, and the internet.