Alcatel-Lucent 6850-48 Hardware Manual

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Roles Within the Stack
Managing OmniSwitch 6850 Series Stacks
page 4-4
OmniSwitch 6850 Series Hardware Users Guide
September 2009
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 
 for more information.
Redundant Management Module Failover (Three or More Switches)
Secondary
Primary
Idle
Idle
Secondary
Offline
Idle
Idle
Primary
Offline
Secondary
Idle
!
Primary
Idle
Secondary
Idle
A stack of four OmniSwitch 6850 Series 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.)
The primary management module in the stack fails or is 
taken offline (e.g., powered off or rebooted by the user).
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.
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.
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