I'm working with old ISDN BRI ports just for the hell of it. I'm using a Cisco 3640 (via NM-1E2W) and a Cisco 1720 router. I researched and researched Cisco's website but can't seem to get solid information on creating a crossover for this particular port type.(It's a BRI-U type not BRI-S/T which means the blue;white/blue pair are the only wires that get crossed) The ports are both Cisco WIC-1B-Us. I created a crossover based on what the datasheet provided as a reference. I connect the cable into the ports but nothing happens. Both ports have been assigned the proper IP addresses and Subnet Masks. Both are turned on. I know they're good cuz I can access them both, but I don't see any LEDs lighting up. The console even displays "Line protocol on Interface BRI0, changed state to down" I know these can be used without an ISP because I learned about them and used them in college before, router to router like what I'm doing. The datasheet also shows these ports are supported for both of my routers. The crossover cable is what's getting me. Does anybody have any idea what I could be doing wrong?