The firmware on the MCT leaf is downloaded.
Enabling maintenance mode on an
MCT leaf involves the Border Gateway Protocol (BGP) and MCT or NSM. The
graceful_shutdown parameter is sent to all the leaf‘s
underlay neighbors (all spines in the pod). The neighbors no longer send traffic
to the MCT leaf going into maintenance mode and redirect traffic from spines to
the peer MCT leaf. MCT instructs the peer leaf to become the designated
forwarder, ICL is shut down, and CCE ports for clients are also shut down.
Traffic from dual-homed servers is redirected to the peer leaf. With maintenance
mode enabled, traffic is completely redirected to the peer leaf.
The
running-configuration is saved on the first MCT leaf to
preserve all current configurations including the maintenance mode enable
configuration.
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.
The
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.
