Hi Nahum,
Each host is expected to have a different SSL Cert
If you are looking to implement CA signed certs for only the ESXi hosts, this should help
VMware KB: Configuring CA signed certificates for ESXi 5.x hosts
or
http://www.derekseaman.com/2013/02/vmware-vcenter-51-installation-part-15.html
Derek's blog also has the procedure for replacing all vSphere certs should you want to go down that path
Regards
a