If you want to use an enterprise or third-party CA-signed certificate, you have to send a Certificate Signing Request (CSR) to the CA.
Use a CSR with these characteristics:
- Key size: 2048 bits or more (PEM encoded)
- PEM format. VMware supports PKCS8 and PKCS1 (RSA keys). When keys are added to VECS, they are converted to PKCS8
- x509 version 3
- For root certificates, the CA extension must be set to true, and the cert sign must be in the list of requirements.
- SubjectAltName must contain DNS Name=<machine_FQDN>
- CRT format
- Contains the following Key Usages: Digital Signature, Non Repudiation, Key Encipherment
- Start time of one day before the current time
- CN (and SubjectAltName) set to the host name (or IP address) that the ESXi host has in the vCenter Server inventory.