Replacing Stack Units

Consider the following points when replacing stack members.

• To replace a unit with a clean unit containing the same modules, simply disconnect the old unit and replace it with a clean unit using the same links. The new unit will be discovered in less than two minutes. No command is needed on the active controller or the clean unit.
• A non-clean unit cannot be discovered by the unit replacement feature. It logs and prints a message when it receives unit replacement probing packets. To convert a unit to a clean unit so it can be discovered by stack zero-touch provisioning or stack interactive-setup, enter the erase startup-config command on the unit followed by the reload command without entering the write memory command.
• Replacing a unit does not cause loops, even when STP is not configured. The reason is that replacing a unit uses the same links that are already configured as stack-ports or stack-trunks.
• If the stack is a ring topology, replacing a unit does not break the stack. The stack becomes linear until the new unit joins to form a ring. If the stack is a linear topology, only the edge unit can be replaced. Replacing a non-edge unit in a linear stack causes other units behind it to become unreachable. The unit replacement could fail because the loss of multiple units causes ambiguity.
• To replace multiple units at the same time, first replace all units and make all physical connections before entering the stack interactive-setup command.