Filius to the Rescue
Trying to get around this issue, I started looking for a network simulator. Everything I found was either too complex (GNS3 or Packet Tracer) or too restrictive (the Teach ICT simulator – OK for KS3.) Eventually I stumbled on Filius, a good midpoint between the two. Filius is an open-source Java app that was written first in German, but then translated into English. There is a decent English guide on the website.
Filius lets you set up a network with computers, switches, routers, and cables. At the most basic level, this can be used to connect the basic components. Each machine can be set up with an IP address, and then the simulation can be run. When in simulation mode, you can install software onto the machines. You can use this to ping between machines and you can see the packets going back and forth as green pulses along the wires, or by right-clicking any computer or router and inspecting the packets as they go back and forth.
Once the basics of a LAN are out of the way, Filius then lets you set up multiple networks, routing tables, web servers and web browsers, email, DHCP, and more. This might all sound a little daunting, especially with classes that are a little less attentive. Fortunately, Filius lets us load and save our networks. For my classes, I prepared networks in advance in order to teach specific concepts. These are now available on the CAS website.
Making it accessible
Adapting the concept of the PRIMM approach, I tried to structure activities to read before writing. Typically, this meant giving students a network already set up with an element of the network working. Students need to predict what the network will do (mostly based on machine names and topology), simulate (run) the network and carry out a few tasks, investigate the settings, modify the settings of a non-working portion to get it running, and then make a new section of the network.
I had success with this approach with my Year 11 class (ages 15–16). Everyone was engaged and it really helped explain the different forms of addressing. Next year, I’ll be breaking the tasks down further so that those that are lower ability can work more independently.