Hi, Harish. The MM Fiber Optic patch cords are not supported for use as stacking cables with X440-G2. However, you can use SFP+ direct-attach cables in lengths of 1, 3, 5, and 10 meters. The
Selecting Stacking Cables table provides a list of cable types that are supported for stacking with Summit and ExtremeSwitching brand switches.
Larry Kunz
Information Development
Extreme Networks