Administration: Stack Management
Unit Failure in Stack
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 68
5
The following shows what happens when a user-assigned, master-enabled unit
with Unit ID 1 joins a stack that already has a master unit with user-assigned unit ID
1. The newer Unit 1 does not join the stack and is shutdown.
User-assigned Master-enabled Unit
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.