We're now taking up network configuration and network services in my operating systems class. As per my parameters, this means setting up a system to act as DHCP server and DNS server among other things, all done via command line. Each student will set up a dual-homed Ubuntu server as a VirtualBox guest. One network interface connects to the outside world, the other network interface connects via VirtualBox internal network to a DSL client, also running as VirtualBox guest.

This configuration raised a dicey problem: how do I turn the Ubuntu server into a router without going through all the gory details of ufw configuration. Personally, I would prefer to run specialized firewall or firewall appliances nowadays, so I don't much bother with ufw or iptables anymore. When I tried revisiting the process with ufw, well, let's just say it made my head spin.

After examining my various options, I ultimately settled on ipmasq, a package that automatically turns an Ubuntu server into a simple router.

To be honest, there's not much more to write about ipmasq. You install it, and wham! the Ubuntu box starts forwarding packets. Not very good from a security perspective, I know, but I do have to take the students to baby steps, and ipmasq does what I want it to do quickly, simply, and with no fuss.