I'm trying to connect a 4500 switch to our existing network. We are connection using 10gig modules. The problem is when we connect the router to the switch the interface starts flapping and error disables itself. I walked the whole path looping the fiber back to the router and have successfully have a link. I even looped the fiber back in the closet both ways and recieve a link light on both the switch and router. When I actually connect the switch to the router I get the flapping problem. I don't think the problem is the fiber..