A stacked switch packet communication system is connected to a Multi-Chassis Link Aggregation Group (MLAG). Devices in the system include a designated device for receiving packets that are destined for the MLAG. A new MLAG device is enabled while continuing packet communication by identifying an address of a single port in the new MLAG device. In first updates of the devices the single port is established in the forwarding databases of the devices and the packets transmitted through the devices to the single port. Thereafter, in second updates the single port is replaced in the forwarding databases by another port of the new MLAG device. Upon completion of respective second updates, the packets are transmitted through the devices to the other port in the MLAG.