Building the network

On the VirtualBox host

In the VirtualBox host the three virtual machines were created. The TrueNAS and desktop computers were assigned an “internal” network interface, each placed on a different network. The gateway router was given three interfaces, two internal one NAT.

The router

Ubuntu was chosen as a server OS because it is capable of what we need, well documented and has a predictable maintenance and release cadence.

The router was installed from the Ubuntu supplied ISO image.

The router’s network interfaces were all configured via Netplan. The external connection was configured to use DHCP.

NAT

A complication is granting Internet access to nodes on the two internal networks. Even though the router’s Internet connection is NAT, VirtualBox will not route packets addressed to the two private subnets.

To grant access we need to make the packets all appear to come from the gateway router. This was achieved by using nftables to perform network address translation on the gateway router’s external interface.

That itself has is behind at least two more NAT routers, inside VirtualBox and on the classroom’s connection, before the publicly addressed Internet.

TrueNAS

TrueNAS was chosen as an application server to try a non-Linux based open source OS. It comes with a web interface built making it easy for us to observe working from the desktop.

The static IPv4 configuration was set up using the text mode interface offered during the initial install from the ISO image.

Ubuntu desktop

Ubuntu desktop was chosen as it is a common and well documented open source desktop OS.

The static IPv4 configuration was set up using the GUI.

DNS

The gateway router does not provide a DNS resolver. To allow the desktop to access websites, it was necessary to configure a DNS server. A public recursive DNS server, 8.8.8.8 was provided in the configuration.