A customer recently asked me “How do I replace the “external” SSL certificate of vCenter but still use VMCA in default mode?” Ever curious, I asked “Why?”. His security team required that any “externally” facing management web pages needed to have a custom certificate that chained up to the corporate PKI. But behind that, they were totally cool with using VMCA in default mode (with the self-generated root certificate) for things like ESXi servers and solution users.