Stack

What is Stack?

Stacking refers to connecting multiple switches that support the stacking function through DAC cables or special stacking cables. In the network topology diagram, these switches will be virtualized into one switch.

Usually only switches from the same manufacturer or even the same model support stacking. As shown in the figure below, this is a common stacking solution. Connect the stacking ports between each switch. Not all ports can be used for stacking. For specific configurations, please refer to the manufacturer's configuration instructions.

Why We Need Stack?

The stacking system allows multiple switches to form redundant backup, as shown in the figure below. When one of switch A or switch B fails, the other can take over the failed device to ensure normal connectivity of the network. After LACP between devices, link redundancy backup can be achieved.

Logically, these multiple devices become the same device, and the number of interfaces is the sum of the number of interfaces of these original devices, which improves the port density and network bandwidth. At the same time, after stacking, you only need to manage one device to perform the overall configuration, which simplifies the operating costs.

How to Stack?

Stacked switches generally have three roles: master switch, backup switch, and slave switch. The master switch is responsible for managing the entire stack system, and there is only one of them. The backup switch is used to take over when the master switch fails. The slave switches are all other switches, which are used for service forwarding.

Take Cisco switches as an example, two devices are stacked, and we configure the priorities of the two switches.

  Configuring stack ports:

The stack is complete. Use the command to check the switch status.

Disadvantages of stack

There are some restrictions on stacking. Only devices of the same manufacturer and model can be stacked. Some devices even require the same system version. After the stack is completed, the system version can only be upgraded one by one, and the devices also need to be unstacked before upgrading, which may cause service interruption.