ufw: Simple Firewalling on Debian and Ubuntu
Enable ufw without losing your SSH session, learn the rule grammar, and see exactly which iptables chains it builds underneath.
Firewall
Stateful inspection, policy design and traffic control at the perimeter. Articles tagged Firewall cover rule structure, NAT interaction and the packet path through the box.
Latest posts
nftables: The Modern Linux Firewall
Your iptables rules already run on nftables. Handles, named sets, inet tables and atomic ruleset loads, all proven with real output from a live lab.
iptables Fundamentals: Tables, Chains, Real Rules
Tables, chains and rule order, demonstrated with real captures from a Debian host in a live lab: DROP against REJECT timing, conntrack, logging and NAT.
ZBF vs ASA vs FTD: Which Firewall Belongs Where
Zone-Based Firewall, ASA, and FTD solve different jobs. This comparison uses real command output captured from all three platforms to show you which Cisco firewall belongs where, not which one is best.
Zone-Based Firewall on Cisco IOS XE: Zones, Zone-Pairs, and the Policy Model
The Zone-Based Firewall is the stateful firewall inside Cisco IOS XE. This anchor guide covers zones, zone-pairs, the class-map and policy-map model, and the default-drop trap that locks engineers out of their own routers.