This page makes use of the tcl/tk toolkit plugin which you can obtain from the here . If you're ready you'll be able to read the ticker on this page: examples. Alternatively you can download the code directly here.
The example tcl/tk application shown here is a simple network creator. You use the mouse buttons as follows:
button-1 - create a node;
button-2 - select a node for joining (or double-button-1);
button-3 - drag a node around;
complete - complete the network (saves lots of laborious connecting up);
shortest path - find the shortest path (pink whilst calculating, orange when finished).
This simple illustration enables you to see how quickly the time taken for a brute-force solution to the shortest-path problem grows with the number of nodes. I suggest you start at 6 and work up. Depending on the power of your machine you should be able to solve 12 to 17 - it can take a very long time!