You may find in the course of updating firmware on your UCS chassis that the primary fabric, goes from fabric A to fabric B. This is no big deal. Any one of those fabric interconnects can act as the primary. However, to appease the sense of 'getting things back to the way they were' and the OCD nature in me, we want to get fabric A back to the primary.
You could just reset fabric interconnect B. But here's a better way:
1. SSH into UCSM
ssh admin@ucsm.mycluster.corn
2. Connect to local management
connect local-mgmt
pdxlab-UCSM2-6120a-B(local-mgmt)#
As you can see from the above command prompt, we are now on FI-B. We want to change this to A:
3. Change cluster lead to A or B
You then run the command:
# cluster lead a
If you are logged in you'll be immediately logged out. If you have the UCS Manager GUI up, you'll immediately lose connection. Do not panic! This is perfectly normal! Your cluster is failing over. Log back in and you'll now be back on A. Nice job! You just failed over your cluster.