Alcatel OS6850-P48 User Guide - Page 168

Roles Within the Stack Managing OmniSwitch 6850/6850E Series Stacks Important Note. For management module redundancy to work effectively, the software on all switches operating in the stack must be synchronized at all times. Refer to "Synchronizing Switches in a Stack" on page 6-39 for more information. Primary Secondary Idle Idle 1 A stack of four switches is operating normally. The stack consists of a primary module, secondary module, and two elements operating in idle status. (The software on all elements in the stack is synchronized.) ! Offline Secondary Idle Idle 2 The primary management module in the stack fails or is taken offline (e.g., powered off or rebooted by the user). Offline Primary Secondary Idle 3 The switch operating as the secondary management module immediately takes over the primary role. Meanwhile, the adjacent switch-previously operating in idle status-now assumes the secondary management role. Idle Primary Secondary Idle 4 If the switch that failed or was taken offline comes back online, it will assume an idle role in the stack. In other words, it will act essentially as an NI module in the virtual chassis, passing traffic via its Ethernet. Redundant Management Module Failover (Three or More Switches) page 6-6 OmniSwitch 6850/6850E Series Hardware Users Guide June 2011