I have a 4510R Device. Also some WS-C3750 Edge Switches connected to them. So if I connect a C3750 Switch to the 4510R Switch an another C3750R Switch to the 4510R Switch and connect both C3750 Switches together I have a loop. I have configures the rapid spanning tree protocol and all works weel and fast. On all Interfaces-Links I have a green LED. Is this right, ore shoud one link-LED be red (the one which his on standby)? thanx alot for your help!