Understanding OpenStack-Contrail Networking Fabric Integration
Contrail Networking Release 2011 supports integrating OpenStack with Contrail Networking Fabric. A Modular Layer 2 (ML2) Neutron plug-in is deployed for this integration. With this integration, you can manage underlay networks for OpenStack compute nodes.
Modular Layer 2 (ML2) Neutron Plug-in
Starting in Contrail Networking Release 2011, the ML2 Neutron plug-in is used to integrate OpenStack with Contrail Networking Fabric. Neutron is an OpenStack project that manages networking between interface devices. The ML2 plug-in enables OpenStack to use various layer 2 networking technologies that are found in complex real-world data centers.
In order to facilitate multi-vendor solutions, Neutron offers the following plug-ins:
Monolithic Plug-in
Modular Layer 2 (ML2) Plug-in
The Monolithic plug-in is no longer supported and is removed from OpenStack. With this release, the only supported plug-in is ML2. For more information on the plug-in, see ML2 Plug-in.
With Contrail Networking Release 2011, the ML2 plug-in is used with Contrail Command UI to facilitate multi-vendor solutions. ML2 plug-in works with Open vSwitch, Linux Bridge, and HyperV layer 2 agents. The ML2 plug-in simplifies adding support for layer 2 networking technologies. This plug-in requires less initial effort to deploy than what would be required to add a new monolithic plug-in.
The ML2 framework offers the following drivers:

Benefits of ML2 Plug-in
The following are the benefits of ML2 plug-in:
Helps in integrating OpenStack with Contrail Networking Fabric.
Used with Contrail Command to facilitate multi-vendor solutions.
Simplifies adding support for layer 2 networking technologies.
Design Overview
This section describes the topology.

Figure 2 depicts the OpenStack Controller, Contrail Networking Controller and the fabric. The Neutron Rest API, ML2 plug-in for layer 2 networking technologies, L3 router plug-in, and the mechanism drivers rests within the Neutron server. The ML2 plug-in mechanism driver (Tungsten Fabric ML2 Driver) and the Tungsten Fabric L3 driver connects the server to the Config API. The connection between the Config API and the fabric is established through the device manager.