Upgrade Wlc's firmware with high-availability AP-SSO enabled

[theophile]

Hello,

We want to upgrade two controllers (5508) in cluster with HA AP-SSO enabled. Could you please give me some recommandations before doing the upgrade? I do not know if all of the APs on the active Wlc will be automatically transfered to the standby one during the upgrade. As both wlcs are located on a critical site, I want to minimize the downtime and want to avoid any problem!

Thanks a lot for your advices

Theo

[Leo Laohoo]

Use "reboot system both". 

Depending on the firmware loaded in the controllers, both GUI and CLI will describe the progress of the upgrade. 

[Andrey_voronkov]

5. After reload the pair, it doesn't work, doesn't start. What to do next?

Isn't the goal of the HA SSO not to reboot at the same time?

[patoberli]

Not in the world of WLC.
Please open a new thread and add the following:
WLC model
Old and new firmware
LED state of the WLC
Any output when connecting a console cable to the WLC