White Papers

• Dell networking OS selects a master switch for the merged stack from the existing masters in the two stacks.
To ensure that one of the two master switches wins the master election in the merged stack, use the stack-unit priority command to
congure the highest priority for the unit (refer to Assigning a Priority to Stacked Switches).
• All the units in the losing stack reboot and then merge with the winning stack that has the stack master.
• If there is no unit numbering conict, the stack members retain their previous unit numbers. Otherwise, the stack master assigns new
unit numbers, based on the order in which they come online.
• The new stack master uses its own startup and running congurations to synchronize the congurations on the new stack members.
NOTE: Adding a new unit that is powered on and has stack groups congured is the same as merging two stacks (refer to Adding
a Stack Unit). If the new unit is congured with a higher priority than the current stack master, it becomes the new stack master
and the stack reloads. If the new unit does not have a higher priority than the master switch, it reboots and is added as a member
switch.
Split a Stack
To split an S5000 stack, unplug the port cables between member units at any time: while the stack is powered on or o and when the units
are online or oine.
Each portion of the split stack retains the startup and running conguration of the original stack.
For a stack that is split into two smaller stacks, each with multiple units:
• If one of the new stacks receives the master and standby units, it is unaected by the split.
• If one of the new stacks receives only the master unit, the master switch retains its role and a new standby is elected.
• If one of the new stacks receives only the standby unit, it becomes the master in the new stack and Dell Networking OS elects a new
standby.
• If one of the new stacks does not receive either the master or the standby unit, the stack is reset so that a new election takes place.
Managing Redundant Stack Management
To manage the redundancy behavior in a stack, use the following redundancy commands.
• Reset the current stack master and make the standby unit the new master.
EXEC Privilege mode
redundancy force-failover stack-unit
A new standby is elected. When the previous stack master comes back online, it becomes a member unit.
• Prevent the stack master or stack unit from rebooting after a failover.
CONFIGURATION mode
redundancy disable-auto-reboot stack-unit
This command does not aect a forced failover, manual reset, or a stack-link disconnect.
• Display redundancy information.
EXEC Privilege mode
show redundancy
Resetting a Unit on a Stack
To reload any of the member units or the standby in a stack, use the following commands.
If you try to reset the stack master, an error message displays: Reset of master unit is not allowed.
• Reload a stack unit from the master switch.
Stacking
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