Stack Management
Unit Failure in Stack
Cisco 500 Series Stackable Managed Switch Administration Guide
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Unit Failure in Stack
Failure of Master Unit
If the Master fails, the backup unit takes over the master role and continues to
operate the stack normally.
In order for the backup to be able to take the place of the master, both units
maintain a warm standby at all times. In warm standby, the master and its backup
units are synchronized with the static configuration (contained in both the Startup
and Running configuration files). Backup configuration files are not synchronized.
The backup configuration file remains on the previous master.
Dynamic process-state information, such as the STP state table, dynamically-
learned MAC addresses, dynamically-learned Smartport types, MAC Multicast
tables, LACP, and GVRP are not synchronized.
When a master is being configured, it synchronizes the backup immediately.
Synchronization is performed as soon as a command is executed. This is
transparent to the user.
If a unit is inserted into a running stack, and is selected as a backup unit, the master
synchronizes it so that it has an up-to date configuration, and then generates a
SYSLOG.
Master/Backup Switchover
When a master fails or when the user configures a force master on the backup unit,
a switchover occurs.
The backup unit becomes the master, and all of its processes and protocol stacks
are initialized to take responsibility for the entire stack. As a result, there is
temporarily no traffic forwarding in this unit, but slave units remain active.
Slave Unit Handling
During the transition of the backup becoming the master, the active slave units
remain active and continue to forward packets based on the configuration from
the original master. This minimizes data traffic interruption in units. After the
backup unit has completed the transition to the master state, it starts initializing the
slave units one at a time by performing the following operations:
