Upgrade Cisco Catalyst 9400 core switches to later IOS version

[JChen522]

I was wondering if anyone can point me to the right direction on upgrading Catalyst 9400 core switches live in production.  What are the general steps and the things to watch out for to keep the downtime minimum?

[justo]

Hello! There is almost too much to deconstruct here in one message...I would recommend first looking at the release notes of your current version and future version. Make sure your redundancy is working as expected (dual supervisors or stackwise virtual) then check back here with any questions in particular

Generally speaking, upgrading on the Catalyst 9k platform has come a long way, and I have found it much more reliable compared to other platforms. Even if everything is fully redundant, still expect that there will be a "blip" in the network.

Cheers.

[JChen522]

Thanks for the quick reply.  I read through the release notes. 

Assuming dual 9400s core/distribution to downlink access switches, fully meshed.  What would be the sequence?

On older releases of IOS, dual supervisors cannot be upgraded together, must be done one at a time which means there will be down time.  One the newer releases, they can be upgraded together? How long will that down time be?

Redundancy is done using stackswise virtual?