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Stack Management
Stack unit priority
Standby controller selection based on priority configuration
You can choose a standby controller by configuring a stack unit with the second highest priority or with the same priority as the
active controller. The standby controller takes over when the active controller fails. If the original active controller becomes active
again, it does not win back its active role, which helps to minimize traffic interruption on the stack. However, if the original active
controller has the higher priority and hitless failover is enabled, the active controller regains its role without resetting other stack
units. If hitless failover is disabled, the active controller resets the other stack units after it regains control.
Two-unit stack controller selection scenario
In a two-unit stack, you can ensure that one unit resumes the active controller role after a reset by assigning it a higher priority.
However, assigning the two units the same priority reduces the number of resets during failover.
The following steps occur on failover when hitless failover is enabled and both members of a two-unit stack are configured with
the same priority:
1.
Unit 1 (the active controller) resets.
2.
The stack fails over to the standby controller (Unit 2).
3.
Unit 1 returns to operation with the role of stack member.
4.
Unit 2 (now acting as controller) sends a stack merge request to Unit 1.
5.
Unit 1 resets and rejoins the stack as the standby controller.
If the active controller has a higher priority than the standby controller in a two-unit stack, the following steps occur:
1.
Unit 1 (the active controller) resets.
2.
The stack fails over to the standby controller (Unit 2).
3.
Unit 1 returns to operation.
4.
Unit 2 (now acting as controller) sends a stack merge request to Unit 1.
5.
Unit 1 resets and rejoins the stack as the standby controller.
6.
Unit 2 schedules a switchover to make Unit 1 the active controller. No unit is reset for the switchover.
Standby controller election criteria
Standby controller election is based on the following criteria:
•
The highest priority
•
Bootup as active controller
•
Bootup as standby controller
•
The lowest boot stack ID
•
The lowest MAC address.
Stack unit priority
A unit with a higher priority is more likely to be elected active controller. The priority value can be from 0 through 255, with a
priority of 255 being the highest. The default priority value assigned to the active controller and standby controller is 128.
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Ruckus FastIron Stacking Configuration Guide, 08.0.90
Part Number: 53-1005572-01
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Troubleshooting
