Cisco SX350 Series Administration Manual page 125

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The devices (units) in a stack are connected through stack ports. These devices are then
collectively managed as a single logical device. In some cases, stack ports can become
members in a stack of Link Aggregation Groups (LAGs) increasing the bandwidth of the stack
interfaces. See Stack Port Link
The stack is based on a model of a single master/backup and multiple slaves.
An example of eight (relevant for the 550 family) devices connected into a stack is shown in
the following:
Stack Architecture (Chain Topology)
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 point of management. 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 (see
- 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, a stack unit loops back the
packets that are supposed to be sent through its failed stacking port, and transmits
the looped back packets through its remaining stacking port to the destinations.
Cisco Sx350, SG350X, SG350XG, Sx550X & SG550XG Series Managed Switches, Firmware Release 2.2.5.x
Aggregation.
Stack Topology).
Administration: Stack Management
Overview