Firewalls and Virtual Private Networks form the foundation of network perimeter security, controlling traffic flow and establishing encrypted communication channels across untrusted networks. Firewalls inspect and filter traffic based on configurable policies, while VPNs create secure tunnels that protect data confidentiality and integrity between remote endpoints. Understanding both packet filtering rules and encryption protocols is critical: a misconfigured firewall rule can expose internal resources, while weak VPN encryption or authentication can compromise entire remote access infrastructures—making proper configuration of both technologies essential for maintaining secure network boundaries in modern distributed environments. In 2026, the perimeter has dissolved: Zero Trust architectures, SASE, and ZTNA are actively replacing legacy VPN-only models, and post-quantum cryptography is entering firewall and VPN products ahead of compliance deadlines.
What This Cheat Sheet Covers
This topic spans 14 focused tables and 116 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Firewall Types
Choosing the right firewall type determines the depth of inspection and the threats you can realistically detect. The field has expanded well beyond stateless packet filters—modern deployments layer NGFWs, WAFs, and cloud-delivered FWaaS to cover every traffic layer and deployment model.
| Type | Example | Description |
|---|---|---|
iptables -A INPUT -s 192.168.1.0/24 -j ACCEPT | • Examines each packet independently based on header information only (source/destination IP, port, protocol) • no connection tracking • fastest but least secure. | |
Session tracking TCP 3-way handshake | • Maintains a state table of active connections, tracking session context (SYN/ACK sequences, connection state) • validates packets belong to established sessions. | |
Palo Alto, FortiGate, Check Point Quantum | Combines stateful inspection with application identification, deep packet inspection (DPI), IPS/IDS, user identity integration, and threat intelligence. | |
Check Point Force, FortiGate with FortiAI | • NGFW with embedded ML and adaptive learning • detects zero-day threats without signatures • continuously trains on live traffic to improve anomaly detection. | |
AWS WAF, Cloudflare WAF, F5 BIG-IP | • Operates at Layer 7, inspecting HTTP/HTTPS traffic • protects against OWASP Top 10 (SQL injection, XSS, CSRF) • sits between users and web applications • not a primary network firewall. |