A switch stack is a set of up to nine Cisco EtherSwitch service modules or Catalyst 3750 switches connected through their Cisco StackWise ports. One of the Cisco EtherSwitch service modules or Catalyst 3750 switches controls the operation of the stack and is called the stack master. It is typically used in the access layer.
Chassis aggregation is a Cisco technology to make two switches operate as a single logical switch. It is similar to switch stacking but meant for chassis switches like the 6500 and 6800 series switches. It is often used in the core layer and sometimes in the distribution layer.
Benefits of switch stacking:
- Simplified network administration: Whether a stackable switch operates alone or “stacked” with other units, there is always just a single management interface for the network administrator to deal with. This simplifies the setup and operation of the network.
- Scalability: A small network can be formed around a single stackable unit, and then the network can grow with additional units over time if and when needed, with little added management complexity.
- Deployment flexibility: Stackable switches can operate together with other stackable switches or can operate independently. Units one day can be combined as a stack in a single site, and later can be run in different locations as independent switches.
- Resilient connections: In some vendor architectures, active connections can be spread across multiple units so that should one unit in a stack be removed or fail, data will continue to flow through other units that remain functional.
- Improving backplane: A series of switches, when stacked together, improves the backplane of the switches in stack also.
Benefits of chassis aggregation:
- For locations needing numerous ports, a modular chassis may cost less.
- With modular switching, there is one enclosure and one set of power supplies. With stackable switching, each unit in a stack has its own enclosure and at minimum a single power supply, but normally two power supplies per switch.
- High-end modular switches have high-resiliency / high-redundancy features not available in all stackable architectures.