Which network defense device is primarily responsible for blocking or permitting traffic based on configured rules?

• A. VPN gateway
• B. Load balancer
• C. Firewall
• D. IDS/IPS

Answer: (C)

Blocking or allowing traffic based on configured rules is the firewall's core capability. A firewall acts as a gatekeeper for networks, inspecting packets and applying a defined set of rules that specify which traffic is permitted or denied by factors like source and destination IPs, ports, and protocols. Stateful firewalls can track ongoing connections to ensure only legitimate return traffic is allowed, while stateless firewalls filter each packet based on fixed criteria. Some firewalls also offer NAT, VPN termination, or application-level filtering, but the essential function remains enforcing access control policies to block or permit traffic. The other options focus on different roles: a VPN gateway provides secure tunnel connections and encryption, a load balancer distributes traffic to multiple servers for performance and availability, and IDS/IPS monitors for threats (with IPS capable of blocking, but primarily as detection/prevention rather than general traffic access control). This makes firewall the best match for blocking or permitting traffic based on rules.