Brocade FastIron Ethernet Switch Stacking Configuration Guide - Manual (Page 97)

Standby controller
In addition to the active controller, another stack member is elected as the standby controller. After a
default interval of 30 seconds, the standby controller takes over if the active controller fails. If hitless
stacking failover is enabled, the standby unit can take over immediately without reloading any unit.
NOTE
Because it can take as long as 20 seconds to age out a neighbor, the standby takeover period may last
up to 50 seconds. Refer to
Port down and aging on page 94.
The standby controller synchronizes its configuration with the active controller at each reset.
Bootup role
When a stack unit boots, it boots in a particular role, such as standalone, active controller, standby
controller, or stack member. When the bootup role is standby controller or stack member, the CLI
available to the unit is limited to show and stack commands. A unit in the role of standby or stack
member will not act without instructions from the active controller. To convert a standby controller or
stack member into a standalone device, use the stack unconfigure me command (refer to
Unconfiguring a traditional stack on page 61).
The last line of the show version output identifies the unit role unless the unit is in standalone mode.
My stack unit ID = 1, bootup role = active
My stack unit ID = 3, bootup role = standby
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.
The following conditions, in the order shown, determine which units will serve as active controller and
standby controller after an election:
• 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, a current active controller
becomes subject to the other factors in this list. The reason for this hierarchy of factors is to
achieve a predictable winner regardless of the boot up sequence for a unit. You can upgrade your
current active controller to "boot as active controller" status by performing a write memory . 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 that 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 (1-8, 1 is the lowest).
• MAC address - The member with the lowest MAC address.
Standby controller
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