My group used to teach Computer Networks at a university ([1] gives a fair overview of the scope if you know Croatian or use a bit of Google Translate). We used CORE and PHP built-in web server [2] for the basic course. IMHO, stuff like Shadow is too overwhelming for the introductory course, but we planned to use it together with ns-3 and SimGrid for the advanced course (which in the end we never got a chance to develop for unrelated reasons).