A stack is the collection of all switches, or units, that are cabled together to form one virtual switch.
One of the switches, called the stack manager, serves as the single point of control for managing the stack. Any stack member can be the stack manager (unless its priority is set to 0).
When the stack is formed, one of the units is selected – either either automatically or using the standby command – as the standby. If the stack manager fails., the standby automatically takes over as stack manager. All of the stack members detect the failure, and the stack continues to forward network traffic with minimal disruption.
All other switches in the stack are stack members. The stack members use stacking technology to behave and work together as a unified system. Layer 2 and Layer 3 protocols present the entire switch stack as a single entity to the network.
For more information about specialized terms used for stacking, see Stacking Terms.