I have a point to point setup and 2 Cisco 1720's (one at each end), for some reason when I connect the routers to the smartjack, the light go green and look good, but it keeps changing from LINK up to down and then up again about every 30 seconds (flapping). Everything is at default, this looks like a layer 1 problem so I havent really done much in the way of configuration. Telco says their stuff looks good. One more side note, I cant ping the serial interface either (from CLI), but if I remove the cable to the smartjack and replace it with a loopback plug it comes up and I can ping it fine. Any ideas?