This read-write enumerated INTEGER (internalonly/internalexternal) defines which category of ports is affected by the cascade-port flow control setting, per the description. Admins use it to scope whether flow control changes apply only to internal stacking links or extend to external ports as well, giving finer control over where congestion management is applied. For example, choosing internalonly ensures flow control changes affect just the stack's internal interconnects without altering behavior on customer-facing external ports.