TOPIC: How to troubleshoot a Back-to-Back cable issue.

I recently purchased 3 Back-to-Back cables from eBay and they do not seem to work. I have tried several different routers and different serial ports to no avail. I have a different B2B cable that I use and the Interface comes to Up and Up. I remove the cable and use any of the newly purchased cables and the interface becomes Down and Down. This seems like it is a cable issue. Is there anything else I can do?

Also, is it bad to yank the serial cable out when the serial interface is up and up and the router is powered on?

Is there anything I have to configure if I connect a cable from an Asynch. serial interface to a Synch. serial? Or does it simply work?