* GRE segmentation mode (in bold): In this mode of operation, Neutron does not require a dedicated 
network adapter.  Neutron builds a mesh of GRE tunnels from each compute node and controller 
nodes to every other node. Private networks for each tenant make use of this mesh for isolated traffic.
 Additionally, your Public network should remain untagged if you consolidate all Neutron traffic to one 
NIC.