Dell FCX624-S Laptop User Manual


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168 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
PowerConnect B-Series FCX hitless stacking
5
Standby Controller role in hitless stacking
In software releases that do not support hitless stacking, the Standby Controller functions as a
dummy device, meaning it provides limited access to the CLI, such as show, stack, and a few debug
commands. The Active Controller can access the full range of the CLI. The Standby Controller
synchronizes its configuration with the Active Controller at each reset.
With the introduction of hitless stacking, the Standby Controller shadows the Active Controller. The
role or behavior of the Standby Controller with hitless stacking is as follows:
The local console on the Standby Controller still accepts only show, stack, and a few debug
commands.
The runtime configuration on the Standby Controller is synchronized with the Active Controller
whenever there is a configuration change.
Protocols are configured in the runtime configuration, but no protocol packets are sent out on
the Standby.
The state of every unit is known, including the state of the Active Controller. The show
commands will display current information, such as STP or port states.
When a failover occurs, the Standby Controller will use its current runtime configuration. The
configuration could be different from the Active Controller if the last configuration transmission
was lost.
After a failover, the new Active Controller (old standby) programs all other units in hardware,
based on its runtime configuration.
Standby Controller election
Candidates for Standby Controller must meet the following criteria:
The unit is operational and the image and module configuration match that of the Active
Controller
The runtime configuration matches that of the Active Controller
The unit does not have a “superior” license compared to the Active Controller. For example, if
unit 2 has a license to run BGP whereas the Active Controller does not, unit 2 has a superior
license and will be allowed to join the stack, but will not be elected as the Standby Controller.
If more than one unit in the stack meets this criteria, the Standby Controller is chosen according to
the following criteria, in the order shown:
Priority – The unit with the highest priority value.
Current standby – The unit that is currently the Standby Controller.
Bootup master – The unit that was the Active Controller before the stack was reloaded.
Bootup standby – The unit that was the Standby Controller before the stack was reloaded.
Once the Standby Controller is identified, the following internal events take place.
1. The Standby Controller is assigned by the Active Controller 30 to 60 seconds after election (60
seconds if the Active Controller boots up in less than 120 seconds).
2. The Standby Controller receives and processes the runtime configuration sent by the Active
Controller.
3. The Standby Controller learns the protocols within 70 seconds.