Backup Switch Selection; Master Failover; Master Recovery; No Backup - Lenovo Flex System Fabric CN4093 Application Manual

Backup Switch Selection

Master Failover

Master Recovery

No Backup

© Copyright Lenovo 2015
An operational stack can have one optional Backup at any given time. Only the
Backup specified in the active Master's configuration is eligible to take over current
stack control when the Master is rebooted or fails. The Master automatically
synchronizes configuration settings with the specified Backup to facilitate the
transfer of control functions.
The Backup retains its status until one of the following occurs:
The Backup setting is deleted or changed using the following commands from

the active Master:
CN4093(config)# no stack backup
‐or‐
CN4093(config)# stack backup <csnum 1‐8>
 A new Master assumes operation as active Master in the stack, and uses its own
configured Backup settings.
 The active Master is rebooted with the boot configuration set to factory defaults
(clearing the Backup setting).
When the Master switch is present, it controls the operation of the stack and
pushes configuration information to the other switches in the stack. If the active
Master fails, then the designated Backup (if one is defined in the Master's
configuration) becomes the new acting Master and the stack continues to operate
normally.
If the prior Master recovers in a functioning stack where the Backup has assumed
stack control, the prior Master does not reassert itself as the stack Master. Instead,
the prior Master will assume a role as a secondary Backup to avoid further stack
disruption.
Upon stack reboot, the Master and Backup will resume their regular roles.
If a Backup is not configured on the active Master, or the specified Backup is not
operating, then if the active Master fails, the stack will reboot without an active
Master.
When a group of stacked switches are rebooted without an active Master present,
the switches are considered to be isolated. All isolated switches in the stack are
placed in a WAITING state until a Master appears. During this WAITING period, all
the network ports of these Member switches are placed into operator‐disabled
state. Without the Master, a stack cannot respond correctly to networking events.
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Chapter 14: Stacking