Can a Cisco 2960S be stacked with a 3560 or 3750?
If possible how?
If not, why not?
The important part: FlexStack is the name of the stacking technology used by the Cisco Catalyst 2960-S series of fixed Ethernet switches. FlexStack is specific to Cisco Catalyst 2960-S switches, and only Cisco Catalyst 2960-S Series Switches use FlexStack.
Longer Answer: No, because they use different stacking protocols and different physical cabling to do so.