Merging Two Operational Stacks

We recommend using the following procedure for merging two operational stacks:
  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 all units in one stack. Connecting a powered-up standalone unit to an existing stack leads to same behavior as when merging two operational stacks. In such cases, the Manager re-election is done based on the rules listed in Stack Manager Election and Re-Election. One of the two managers wins the election and the losing stack manager reboots itself and all its member units. After the reboot, all of the losing stack members join the winning stack to form a single stack. The winning stack remains functional through the merge process. If the stack merge is performed in this way, then we strongly recommend setting the priority of the desired winner stack manager to a higher value than the stack manager that should lose the election.