Brocade FastIron Ethernet Switch Stacking Configuration Guide - Manual (Page 54)

Traditional stack unit identification
Stack units are identified by numbers 1 though 8. You can display stack unit IDs by entering the show
stack command.
A new device (one that has not been connected in traditional stack or has not been manually assigned
a stack unit number) ships with a default number of 1. Once you enable stacking and the unit becomes
part of a traditional stack, its default stack unit number changes to the lowest available number in the
stack. You can configure the stack suggested-id command in a standalone unit before it joins a stack
to assign this unit the suggested ID.
Stack units must each have a unique identification number. Every stack member, including any
standalone units, retains its stack unit number unless that number is already being used in the stack,
or until you manually renumber the unit using secure-setup. For more information about how to
renumber stack IDs using secure-setup, refer to “Renumbering stack units.”
Traditional stack unit priority
A unit with a higher priority is more likely to be elected active controller. The priority value can be 0 to
255 with a priority of 255 being the highest. The default priority value assigned to the active controller
and standby is 128.
You can assign the highest priority value to the stack unit you want to function as the active controller.
When you enter a new priority value for a stack unit, that value takes effect immediately, but does not
affect the current active controller until the next reset. However, if you enable hitless stacking
failover, the stack unit with the highest priority will become the active controller in about five minutes
(2 minutes in the case of ICX 6430 devices).
You can give your active and standby controllers the same priority, or different priorities (active
highest, standby second-highest). When active and standby controllers have the same priority, if the
active fails and the standby takes over, then the original active becomes operational again, it will not
be able to resume its original role if the new active controller has more members.
In the same situation, when the priorities of the active and standby controllers are different, the old
active controller will regain its role and will reset the other units.
For example, suppose both active and standby controllers have the same priority. If there are more
than two units in a stack and the active controller leaves and comes back, it cannot win back the active
role because the new active controller has more members than the old active controller, which has no
members. In this case, both the old active controller and new active controller have no members, so
the unit with the longer up time wins the active role. If the old active controller is reset, it cannot win. If
the old active controller is not reset, it could win due to longer up time on up time or lower unit ID.
When the active controller and standby controller have the same priority, the system allows a stack
switchover if the hitless-failover enable command is configured. It is used to switch the role between
the active controller and standby controller without traffic interruption.
If you want to assign the same priority to the active and standby controllers, you must do so after the
stack is formed. This prevents the intended standby controller from becoming the active controller
during stack construction.
Changing the priority of a stack member will trigger an election that takes effect immediately unless
the active controller role changes. If this is the case, the changes will not take effect until after the next
stack reload. However, if you enable the hitless stacking failover command, the stack unit with the
highest priority will become the active controller without reload.
To display stack member priority values, enter the show stack command.
device(config-unit-3)# show stack
alone: standalone, D: dynamic config, S: static config
ID Type Role Mac Address Pri State Comment
Traditional stack unit identification
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