Continuing the series of Linux Networking, we are going to do a refresh on DNS. We will start from the plainest possible fact — a machine is reachable by its address — and work our way up through /etc/hosts, nsswitch.conf, /etc/resolv.conf, a real DNS server we run ourselves, the recursive hierarchy that answers queries for the rest of the internet, the record types you actually meet in the wild, and the tools you use when any of it goes wrong.
In a previous tutorial we talked about network routing. Now we are going to discuss Linux network namespaces. We will start with two namespaces that can’t even ping themselves, connect them with a virtual cable, replace that cable with a bridge, give the host a leg on that bridge, and then work our way outward - routing, forwarding, NAT, route specificity, and finally port forwarding back in. Everything is done by hand with ip and iptables to exercise the concepts.
In this tutorial we are going to do a refresh on routing in Linux networking. To simulate an environment we will use Linux machines via Lima and the limactl CLI. We will create two virtual machines on two different virtual networks and establish communication between them via a router - a third virtual machine.