As a side note, based on your diagram above, your APICs connectivity is something that could be a concern. Typically when you upgrade a fabric you'll perform the switch upgrades in an Odd/Even manner. This assumes that every other Leaf is in a VPC pair. When combined with the practice of dual connecting your end hosts to a VPC pair whenever possible (Leaf1_2, Leaf3_4 etc), you ensure that one leaf will remain online during an upgrade. The way you have your APICs connected doesn't follow this. Should you upgrade "odd" Leafs according to above, you'd completely lose APIC1 during the process. Though APIC2 & 3 would remain reachable in this case, I would advise a more resilient design and avoiding Cluster disruption if/when possible. Of course, you could manually perform Leaf Upgrades in any order and make the above work, the most deterministic & common is the Odd/Even method - so just wanted to call this out.