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The general idea in OpenStack is that Neutron manages L3 routing, allowing security groups (firewall), load balancing and other L3 features available via SDN solutions (OVS and Hyper-V networking in our case).

Here's the “usual OpenStack way” to have a VM connected to 2 networks, one internal and one external:

• Create a new network in your tenant (demo or else, not admin), call it e.g. "local". Do not attach it to a router.
• Boot a VM with two nics: one on "private" and one on "local"

The first NIC on “private” will be natted and routed externally through “public”. The second NIC on “local” will be internal only (not routed).

Said that, there’s also an alternative (which I wouldn't recommend, but it's good to know it's available):

• create a Neutron flat network associated to an external switch on your hyper-v host (needs a network_provider mapping).
• Boot a VM attached to that network using fixed IPs (unless you want to let Neutron handle the DHCP on your physical network)

This way the VM will skip completely the Neutron routing and be directly connected to your physycal network.

here's an example on how to do the Neutron side of the configuration: https://developer.rackspace.com/blog/neutron-networking-simple-flat-network