This read-write INTEGER lets an admin configure which trunk a stacking port will join once the device is reset, taking effect only after that reset, with zero meaning it will not be a trunk member. An admin restructuring stack trunking uses this to stage a trunk-membership change that will not disrupt the currently active stacking links until a planned reset actually applies it. For example, an admin planning to move a cascade port into a different trunk group writes the new trunk ID here ahead of a scheduled maintenance-window reboot, so the change takes effect cleanly at that reset rather than immediately.