my wish with Proxmox would be:
Have some virtuell Server KVM and OpenVZ and reach them with IPv6
The Proxmox Host (Server) itself dont't need IPv6, he will only be reached in a local Network with a Privat IPv4

the Question was/is how to do it:

So what nedd to be configured on the Proxmox Server?

And what need to be configured on the KVM and the openVZ Server?