Lesson 2 of 412 min

Firewalls — the boundary

Inbound vs outbound, NAT (Network Address Translation), port forwarding, DMZ (Demilitarized Zone), IPS (Intrusion Prevention System). Fortinet/SonicWall/Sophos vocabulary.

Notebook and laptop with structured documentation — Photo by Christina Morillo on Pexels

Stateful firewalls track connections — outbound requests get matching inbound replies allowed automatically.

Port forwarding (DNAT) lets external traffic reach an internal service. Use sparingly; replace with VPN (Virtual Private Network) or Zero Trust when possible.

Diagram · Small-office network

IPS (Intrusion Prevention) inspects payloads, not just ports. Modern UTM/NGFW (Next-Generation Firewall) devices combine firewall + IPS + content filter + VPN.

Key takeaways

▸Stateful = remembers the conversation
▸Port forwards are technical debt
▸NGFW = firewall + IPS + content + VPN in one box

Areas to show initiative · +15 XP each

Audit firewall rules for any client; flag the 'allow any-any' ruleDocument every port forward and what it's for

Next: Group Policy that doesn't make you cry →