From the documentation:
OpenNebula will add by default a one-- prefix to the name of the vCenter VMs it spawns, where is the id of the VM in OpenNebula. This value can be changed using a special attribute set in the vCenter cluster representation in OpenNebula, ie, the OpenNebula host. This attribute is called VM_PREFIX (which can be set in the OpenNebula host template), and will evaluate one variable, $i, to the id of the VM. A value of one-$i- in that parameter would have the same behavior as the default.
IP addresses can be set in imported vCenter networks using address spaces.