Hi, I'm studying for the CCNA and I am having a great deal of trouble with ISDN and BRI. I think it would help me to have some physical Cisco ISDN/BRI hardware and actually set it up, get it working, and then intentionally misconfigure and break various pieces to see what that looks like from the router console.
On eBay I have found Cisco 2503 routers w/ BRI interfaces. I have also seen Cisco routers with NT1 interfaces. Can either of these be configured back-to-back with a specific cable? Or, can you configure a third router to simulate an ISDN switch, like you can configure a router to simulate a frame relay switch? I have several spare 2501s and 2514s.
If I can get pointed in the right conceptual direction I can research it from there. I'm just not clear on the components needed for an ISDN LAB.