Just recently we can across a big with having a mixed MS425-16 / MS425-32 stack.
We set up the stack in our workshop and it worked fine. It was then moved to our server room and was still working fine. Ports 17 and 18 (qsfp) on the MS425-16 were configured as stack ports and and 33 and 34 qsfp) were configured as stack ports on the MS425-32.
When the MS425-16 switches were powered down and moved, on powering back up the agreggated port configuration from ports 17 and 18 from the MS425-32 was applying to ports 17 and 18 on the MS425-16.
We were getting LACP errors on the MS425-16 switches even though they were configured as stack ports. Meraki support confirmed this was happening and when the agreggated configuration on the ports of the MS425-32 was removed and MS425-16s were rebooted they joined the stack successfully.
However we had aggregated ports set up on the remaining lower ports of the MS425-32 and they seemed to apply to the agreggated ports of the MS425-16 switches. We started to get stp errors on the MS425-16 ports, blocking and also errors on the lag setup in our HPE Synergy enclosure.
The issue went away when the MS425-32 switches were powered off. At this stage we are waiting on Meraki support to supply more information about the bug and assist with how to remedy this.
I would like to find out if anyone else has experienced this and if they have been able to implement the mixed stack. Were you able to use an older firmware or rebuild the stack to fix this?
The safest option at this stage seems to run 2 stacks and not mix the switches, however this would mean that we couldn't use them as one core switch as we intended.
Fortunately this was our DR site and apart from 2 circuits to sites, everything was in maintenance.
Equipment was only connected to the MS425-16 switches and I had scheduled to move equipment to the MS425-32 the following day. If I had done this the other way arround I would may have only found the issue on the 2nd day of work and caused greater issues.
So, once the MS425-32 switches were disconnected we were able to bring the 2 sites back online and remove our equipment from maintenance. I then cancelled the following days work.
When we have a plan to correct the issue with the MS425-156 / 32 stack I will schedule to reinstate the MS425-32 switches. I will post an update on how we proceed.