I have three UCS C210 M2 servers running my CUCM 8.6.2, Unity Connection, and Contact Center Express. My VM administrator would like to upgrade our ESXi host to the latest version (5.5.1a) to correct the heartbleed vulnerability. I can't seem to find any documentation that goes higher than ESXi 5.1. My question is has anyone upgraded to ESXi 5.5.1a on a similar platform and if so were there any issues that needed to be addressed?