The blog surveys 7 configuration changes to transform a multi-homed Linux host into a switch or router: activating IP forwarding, defining bridges, nftables policies, stateful firewalling with conntrack, NAT and masquerade policies, DHCP/DNS with dnsmasq, and WiFi with hostapd.

It explains packet processing in the Linux kernel networking stack, including netfilter hooks at PREROUTING, INPUT, FORWARD, OUTPUT, and POSTROUTING stages. IP forwarding is enabled via net.ipv4.ip_forward=1 in /etc/sysctl.d/, allowing packets to reach the FORWARD hook instead of being dropped.