Please confirm the sequence of events
1) You initially upgraded secondary FI and when you activated it, secondary FI along with IOMs attached to it came up successfully with upgraded version. Is this correct ?
2) Then you made upgraded ( secondary ) FI as primary by issuing " cluster lead " command from operating primary.
3) Initiated upgrade on old primary. Then activated new version.
Now servers lost connectivity.
Is my understanding correct ?
1) Did all servers lose connectivity ( if you have multiple chassis ) ?
2) If not, do you know list of servers that lost the connectivity ?
3) Both LAN & SAN or only LAN or only SAN connectivity ?
4) Did you make any changes to resolve the issue ? If not, how did the connectivity got restored ?
I would suggest to you open a TAC SR with above information and UCSM and corresponding chassis tech support bundle.
Please include approx date / time of the event.