This article provides the steps and CLI commands used to perform a hitless software upgrade on controllers.

Be sure to schedule downtime for completing this process (Off-hours is recommended).

1. In Primary/Secondary, controllers save the current configuration as "Save Configuration". In Member, controllers save the current configuration as "Save Configuration Local" in the CLI of the controllers.

   MX-200# show system                               (to confirm the current MSS Code Version)
   MX-200# save configuration                      (on Primary / Secondary controllers)
   MX-200# save configuration local             (on Members controllers)

2. Copy the downloaded MSS version from a TFTP server to boot partition 0/1 in non-volatile storage of the controllers (Primary, secondary and Members).

   To copy system image from a TFTP server to boot partition 1 in nonvolatile storage, type the following command in the CLI of the controllers (Primary, secondary and Members):

   MX-200# copy tftp://<TFTP_IP>/<Type the filename saved in tftp directory> boot1: <Type the filename to be saved in nonvolatile storage>
   
   Note: To copy image from a TFTP server to boot partition 0 then set boot0, use the above mentioned command.

3. After installing the Image in all the controllers (Primary, secondary and Members), type the following command to set the boot partition to boot0/boot1 in the CLI of the controllers (Primary, secondary and Members).
   
   MX-200# set boot partition boot0/boot1

   A message will appear eg: success: Boot partition set to boot0:WC080202.8XX (8.0.2.2.0)

   Note: Set the boot partition appropriately in all the controllers.

4. On the Primary controller,  type the following upgrade command:

   MX-200# Upgrade Cluster
   
   Note: After entering the upgrade command in the CLI of Primary controller, all of the Secondary and Member controllers will be updated to the same MSS version.

5. After the upgrade, check the status and the complete configuration.
   Note: The upgrade process will cause the controllers and AP’s to reboot. The clients will also disconnect.

6. Check whether all AP's are up and in operational mode. Use the following commands on the CLI interface of Primary controller.

   MX-200# show mobility-domain
MX-200# show ap status
MX-200# show sessions

You can upgrade controllers from 8.0 to 9.0 MSS version by following the same hitless software upgrade steps above.

The following image illustrates the complete upgrade workflow: