Upgrade firmware for a switch stack

[genevieve]

Hello

It's a simple question, I have a stack of 3 switch, 2 NetVanta 1638 and 1 NetVanta 1638P. my firmware is R10.9.4 (yes it's very old). 

What is the best way to upgrade my firmware ? upgrade the stack or individually or each switch ?

thanks for your help

[BradR]

Are you running Active Chassis with the switches or are they just interconnected? There is quite a few changes from that firmware as latest release is R13.10. I would make backups of configs and plan for some downtime and upgrade all at the same time.

[genevieve]

thanks for your answer, it was just interconnected. 

thanks !

[genevieve]

but will I upgrade the stack or individually each switch ? and If I it's individually how ?

Thanks,

[BradR]

You will upgrade each switch individually. Below is a document that describes the multiple ways you can upgrade firmware for AOS products.

https://supportcommunity.adtran.com/t5/General/Upgrading-Firmware-in-AOS/ta-p/27008 

[irritatedtech]

I cannot find documentation regarding stacking (Activ Chasis) 1550 or 1560 Netvanta.  

can you help?