Merging traditional stacks

Traditional stacks may be merged, but the total number of stack units must not exceed the maximum stack supported by the device. For example, you could combine two stacks of ICX 7750 devices with four units each into a single stack of eight units.

NOTE
You cannot use secure-setup to merge stacks because secure-setup does not work across stack boundaries.

You can merge stacks by connecting them together using the stacking ports. Before doing this, make sure that no stacking ports (for example, ports on an end unit in a linear stack topology) have been reconfigured as data ports.

When stacks are merged, an election is held among the active controllers. The winning controller retains its configuration and the IDs of all of its original stack members. The remaining stack units lose their configuration and are reset. If the IDs of the losing stack units conflict with the IDs of the winning units, they may change, and the IDs will no longer be sequential.

NOTE
You can use secure-setup to renumber the members in the newly merged stack. Refer to Renumbering stack units for more information.

The following examples show how stack merging works:

  • If a stack partitions into multiple stacks because of a connection failure, you can fix the connection and the stack partitions will merge back into the original stack with no change to stack IDs because all stack IDs are distinct.
  • In a linear stack topology, the end units of the stack have only one stacking port configured. Before you can merge two linear stacks, you must reconfigure the end units so that both ports are stacking ports.