4. The switch with the lowest MAC address. The factors for electing or reelecting a new standby switch are same as those for the active switch election or reelection, and are applied to all participating switches except the active switch. Note After election, the new active switch becomes available after a few seconds. In the meantime, the switch stack uses the forwarding tables in memory to minimize network disruption. The physical interfaces on the other available stack members are not affected during a new active switch election and reset. When the previous active switch becomes available, it does not resume its role as the active switch.
If you power on or reset an entire switch stack, some stack members might not participate in the active switch election. Stack members that are powered on within the same 2-minute timeframe participate in the active switch election and have a chance to become the active switch. Stack members that are powered on after the 120-second timeframe do not participate in this initial election and become stack members. For powering considerations that affect active-switch elections, see the switch hardware installation guide. As described in the hardware installation guide, you can use the ACTV LED on the switch to see if the switch is the active switch.
Switch Stack Configuration Files The active switch has the saved and running configuration file for the switch stack. The standby switch automatically receives the synchronized running configuration file. Stack members receive synchronized copies when the running configuration file is saved into the startup configuration file. If the active switch becomes unavailable, the standby switch takes over with the current running configuration. The configuration files record these settings:
• System-level (global) configuration settings such as IP, STP, VLAN, and SNMP settings that apply to all stack members • Stack member interface-specific configuration settings that are specific for each stack member The interface-specific settings of the active switch are saved if the active switch is replaced without saving the running configuration to the startup configuration. Note A new, out-of-box switch joining a switch stack uses the system-level settings of that switch stack. If a switch is moved to a different switch stack before it is powered on, that switch loses its saved configuration file and uses the system-level configuration of the new switch stack.
If the switch is powered on as a standalone switch before it joins the new switch stack, the stack will reload. When the stack reloads, the new switch may become the active switch, retain its configuration and overwrite the configuration files of the other stack members. The interface-specific configuration of each stack member is associated with the stack member number. Stack members retain their numbers unless they are manually changed or they are already used by another member in the same switch stack. If the stack member number changes, the new number goes into effect after that stack member resets.
• If an interface-specific configuration does not exist for that member number, the stack member uses its default interface-specific configuration. Managing Switch Stacks Switch Stack Configuration Files Managing Switch Stacks 6