Redundant distribution switches (stacked): how to upgrade without impact?

[jeronimo]

Hi all,

If you want to eliminate Spanning Tree from the edge redundantly connected to the distribution, the two solutions AFAICS are to :
1) configure the distribution switches to be a stack/virtual chassis, or
2) use MLAG.

Let's assume we use stacking because that is the easier way to manage the entire thing.

How would we be able to upgrade the two stacked distribution switches in some sort of rolling upgrade? (X460-G2 with EXOS 21)

Can we force one to be master, disable the second (except for management), then upgrade and reboot the second one, promote it to master, and then do the same thing with the first?

Is there *any* procedure at all that would accomplish this? If no, what solutions are there (except for MLAG) with spanning tree not being an option?

Thanks,
Marki

[dflouret]

Marki,

When you upgrade the firmware in a stack the Master takes care of downloading the image to all switches in the stack but to make that new image active the whole stack has to be rebooted. No phased approach here.

In MLAG, on the contrary, you can update the image in both members of the MLAG and then reboot one of them and then the other one. While one switch is rebooting, the other will take care of all the traffic, with no loss of communication.