The firmware on the MCT leaf is downloaded.
Enabling maintenance mode on one of the leafs in the centralized MCT leaf pair follows the same behavior as the MCT leaf pair in a Clos topology. The only difference is the iBGP Layer 3 backup link between MCT leaf pairs. Maintenance mode results in the traffic being redirected to the peer leaf in the centralized MCT leaf pairs.
running-configuration is saved on the first MCT leaf to
preserve all current configurations including the maintenance mode enable
The device is rebooted for firmware activation without traffic loss.
After the firmware is upgraded, the maintenance mode is disabled to allow traffic again through the upgraded MCT leaf.
running-config is saved again to ensure the maintenance
mode config remains disabled.
The same process can be carried out on the second MCT leaf to upgrade the firmware without traffic loss.