Cisco 500 series Administration Manual page 63

Stack Management
Overview
Cisco 500 Series Stackable Managed Switch Administration Guide
The stack is based on a single master/backup and multiple slaves model.
An example of four devices connected into a stack is shown in the following:
Stack Architecture
A stack provides the following benefits:
• Network capacity can be expanded or contracted dynamically. By adding a
unit, the administrator can dynamically increase the number of ports in the
stack while maintaining a single, logically-managed device. Similarly, units
can be removed to decrease network capacity.
• The stacked system supports redundancy in the following ways:
- The backup unit becomes the master of the stack if the original master
fails.
- The stack system supports two types of topologies: chain and ring. In
ring topology, if one of the stack ports fails, the stack continues to
function in chain topology.
- A process known as Fast Stack Link Failover is supported on the ports in
a ring stack to reduce the duration of data packet loss when one of the
stack ports link fails. Until the stack recovers to the new chain topology,
the stack port that is currently down, loops back the packets that were
supposed to be sent through it, so that the packets arrive at their
destination using the remaining stacking links. During Fast Stack Link
failover, the master/backup units remain active and functioning.
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