For OpenNebula version <5, see here: https://github.com/OpenNebula/addon-eywa
I have installed and began working with the above mentioned addon. However, either it is lacking support for v5+ or simply does not work as intended anymore. I think that the OpenNebula project would greatly benefit from a built in solution much like the above example. What I specifically would like to see is a model similar to OpenStack for tenant networking (without the headache that is openstack, of course). Tenants should be able to define their own internal networks, routers, etc.
I would volunteer to test any new addon like this on my systems.