Understanding Switch Stacks

A switch stack is a set of up to four Ethernet switches connected through their stacking ports. One of the switches controls the operation of the stack and is called the stack manager. 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.

The stack manager is the single point of stack-wide management. From the stack manager, you configure:

  • System-level (global) features that apply to all stack members
  • Interface-level features for all interfaces on any stack member

A switch stack is identified in the network by its network IP address. The network IP address is assigned according to the MAC address of the stack manager. The MAC address used by the switch is the MAC address of the manager. You can see this address by issuing the show network command. Every stack member is uniquely identified by its own stack member number.

All stack members are eligible stack managers. Exception: Setting a stack member‘s priority to 0 (zero) makes it ineligible for manager selection. When the stack is formed, one of the units is automatically selected as the standby for the stack. The standby of the stack takes over as manager if the current manager fails. The standby of the stack can also be configured using the command standby unit-number.

The stack manager contains the saved and running configuration files for the switch stack. The configuration files include the system-level settings for the switch stack and the interface-level settings for all stack members. Each stack member retains a copy of the saved file for backup purposes.

If the manager is removed from the stack, the standby of the stack will take over and will then run from that saved configuration.

You can use these methods to manage switch stacks: