Gateway-less underlay connectivity

For simple Enterprise use cases and public cloud environment, it is advantageous to directly route packets using IP fabric network without a need for SDN gateway. The primary reason for contrail in this mode is to manage distributed security policy for workloads or baremetal servers.

The following use cases have to be supported:

1. VMs / containers spawned in the IP Fabric network communicating with each other using only underlay (no tunneling).

2. Virtual networks having IP subnet which is a subset of the IP fabric network or a different subnet and using IP fabric network as the provider network. VMs / containers from these VNs communicate within their VNs, with IP fabric VN and with other VNs which also have IP fabric as their provider network based on policy configured, using only underlay (no tunneling).

3. Virtual networks having IP fabric VN as their provider network communicating with other VNs which do not have any provider network configured based on policy configured, using overlay (with tunneling).

4. Vhost communication with other compute vhosts and with VMs / containers in IP fabric network or other VNs having IP fabric network as their provider network based on policy configured, using underlay (no tunneling).