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Stacking Dell PowerConnect 7000 Series Switches
Page 18
Merging Two Operational Stacks
The recommended procedure for merging two operational stacks is as follows:
Caution! This procedure is disruptive and requires a network outage.
1. Always power off all units in one stack before connecting to another stack.
2. Add the units as a group by unplugging one stacking cable in the operational stack and
physically connecting all unpowered units.
3. Completely cable the stacking connections, making sure the redundant link is also in place.
Two operational stacks can also be merged by reconnecting stack cables without powering down units
in either stack. Connecting a powered-up standalone unit to an existing stack leads to same behavior as
when merging two operational stacks. In such cases, manager election is performed and the manager
unit with the higher MAC address is chosen as manager. The stack that no longer has a stack manager
resets itself and all of its member units. After the reset, all the stack members in the reset stack join
the stack that has the manager to form a single stack. The stack that has the manager remains
functional through the merge process.
Synchronizing the Running Configuration between the
Master and Standby Units
The master unit copies its running configuration to the standby unit whenever the configuration
changes (subject to some minimal time delays introduced in the copy mechanism to increase the
efficiency of the transfer process). This enables the standby unit to take over the stack operation with
minimal interruption if the master unit becomes unavailable.
The running-config synchronization also occurs:
• When the administrator saves the running configuration to the startup configuration on
the master unit.
• When the standby unit changes.
Master Failover
If the current master unit fails, the standby unit becomes the master unit. If no switch is preconfigured
as the standby unit, the firmware automatically selects a standby unit from the existing stack units.
When the failed master resumes normal operation, it joins the stack as a member (not a master) if the
new master unit has already been elected.
The stack supports nonstop forwarding and graceful restart during a master failover. See “Nonstop
Forwarding” on page 22.
Effect of Master Failover on PoE Devices
Stack members that provide power-over-Ethernet (PoE) to connected devices continue to provide
power in the event of a master failover. The PoE application uses a separate controller on each unit,
and these controllers are not initialized upon a warm restart.