I have a 2611 with a 1T WIC connected to a 2521's async serial port, however the status on both ends for the interface is always "down/down".
I've ruled out the cable being bad by connecting it to serial0 (sync port) on the 2521 and it went right up. I don't think the serial2 (the async port) is bad because it passes POST and I get the same results if I try it on serial3 (another async port). I've double checked the DCE end of the cable is plugged into the frame relay switch and the DTE end is on the 2611.
I've tried changing the port to run in sync mode with "physical-layer sync" and restarting both routers, but it stays in "down/down". Am I missing something?
The frame relay switch is running IOS 11.3(11a).
Attached are a couple files with some output and the frame relay config file.