I am new here so PLEASE forgive my ignorance. I am looking for an inexpensive isdn solution to connect about 20 of routers with bri u interfaces to a central site router for dial-on-demand routing. It is a classroom setup to teach techs networking. I have looked at purchasing an Adtran switch but the boss says no way, too expensive. I have seen that I could build an isdn pbx to handle the switching, but can anyone point me in a direction where to start? Basicly I have 20 routers w/bri u interfaces dialing a central router with 1 pri interface which routes to my central site network. I currently am borrowing 20 real bri and one real pri from the IT guys who want them back. Dan