configuring-firewallslisted

# Configuring Firewalls ## Purpose Guide engineers through configuring firewalls across host-based (iptables, nftables, UFW), cloud-based (AWS Security Groups, NACLs), and container-based (Kubernetes NetworkPolicies) environments with practical rule examples and safety patterns to prevent lockouts and security misconfigurations. ## When to Use This Skill **Trigger Phrases:** - "Configure firewall for [server/service]" - "Set up security groups for [AWS resource]" - "Allow port [X] through firewall" - "Block IP address [X.X.X.X]" - "Set up UFW on Ubuntu server" - "Create iptables/nftables rules" - "Configure bastion host firewall" - "Implement egress filtering" **Common Scenarios:** - Initial server setup and hardening - Exposing a new service (web server, API, database) - Implementing network segmentation - Creating bastion host or jump box - Migrating from iptables to nftables - Configuring cloud security groups - Troubleshooting connectivity issues ## Decision Framework: Which Firewall Tool? ### Cloud Environments **AWS:** - Instance-level control → **Security Groups** (stateful, allow-only rules) - Subnet-level enforcement → **Network ACLs** (stateless, allow + deny rules) - Use both for defense-in-depth **GCP:** - Use **VPC Firewall Rules** (stateful, priority-based) **Azure:** - Use **Network Security Groups** (NSGs) (stateful, priority-based) ### Host-Based Linux Firewalls **Ubuntu/Debian + Simplicity:** - Use **UFW** (Uncomplicated Firewall) - recommended f