Active controller and standby controller elections

Whenever there is a topology change in the stack (a reset, unit failure, or the addition or removal of members), elections are held to determine the status of the active controller and standby controller. The results of the election take effect after the next stack reset.

Certain conditions, in a particular order, determine which units serve as active controller and standby controller after an election. The hierarchy of factors achieves a predictable winner, regardless of the boot up sequence for a unit.

Active and standby controller elections are determined in a slightly different way when hitless failover (the default) is enabled. The order reduces traffic interruptions during unit reset.

• Boot as active controller - Indicates that a unit was previously active controller before the current boot sequence and will again assume the role of active controller when two standalone units are combined into a stack. When a third standalone unit joins the stack, the current active controller becomes subject to the other factors in this list. You can upgrade your current active controller to "boot as active controller" status by executing the write memory command. The system interprets the write memory action as a directive to maintain the current active controller role regardless of resets or a new unit joining the stack.
• Greater number of members - The unit that has control over the greater number of stack members.
• Failover unit - In a two-unit stack, the unit that is active controller after a failover and has an up time of more than 10 minutes, when the second unit has an up time of less than three minutes.
• Priority - The unit with the highest priority value.
• Longer up time - The unit with the longest up time if the up time is at least 30 seconds longer than for any other unit. When up times are compared, there is no effect if the difference is less than 30 seconds.
• Lowest boot stack ID - The unit that has the lowest boot stack ID. Unit ID 1 is the lowest. The unit ID may be 1 through 8 (or 1 through 12 for ICX 7250, ICX 7450, or ICX 7750 devices).
• MAC address - The member with the lowest MAC address.

When hitless failover is disabled, the following factors, in the order shown, are used to determine active and standby controllers.

• Boot as active controller - Indicates that a unit was previously active controller before the current boot sequence and will again assume the role of active controller when two standalone units are combined into a stack. When a third standalone unit joins the stack, the current active controller becomes subject to the other factors in this list. You can upgrade your current active controller to "boot as active controller" status by executing the write memory command. The system interprets the write memory action as a directive to maintain the current active controller role regardless of resets or a new unit joining the stack.
• Priority - The unit with the highest priority value.
• Greater number of members - The unit that has control over the greater number of stack members.
• Longer up time - An up time that is more than 30 seconds longer than the next one in size is considered. Where up times are compared, there is no effect if the difference is less than 30 seconds.
• Lowest boot stack ID - The unit that has the lowest boot stack ID. Unit ID 1 is the lowest. The unit ID may be 1 through 8 (or 1 through 12 for ICX 7250, ICX 7450, or ICX 7750 devices).
• MAC address - The member with the lowest MAC address.