There is a need from Service providers to create services for customers that could
a) be deployed in a timely matter (seconds rather than months
b) Lower Op Ex through automation
c) reduce Operational complexity with template configs
Contrail is a module that can be currently added to an Openstack or Cloudstack platform. I'll talk about the Openstack implementation as I know more about this Cloud platform. The Contrail Controller works entirely in the overlay. It does not know anything about the underlay except for the gateway so it expects the physical network to already be in place. This means it can interoperate with any existing switch vendor network. When you install Contrail as a Neutron plugin into Openstack, it will create a vRouter which is bound to the hypervisor. Currently KVM is the one it works with but I hear that it was tested on VMware as a vm but not directly onto ESXi. The vRouter is important because you wouldn't use Open vSwitch (OVS). The main function of Contrail is creating the overlay network within Openstack.
Here's how this works. Let's look at this simple logical topology
First you would go to the Contrail Controller (Web GUI) and create the two networks.
Then you would go to the Openstack Horizon Web UI and spin up your VM instances. Under the networking tab you should be able to associate the network to the VM.
Next you would need to create a policy so that each network can talk to each other. Think of it as creating a firewall ACL.
Contrail will automatically assign the VM an ip address and point the default route of the VM to the vRouter.
This will allow you to access the Back End Server.
Overall provisioning time would be roughly 2-3 minutes depending on how fast the VMs can spin up.
Now if you want to provide access to anything outside of the Data Center you'll need to go through a gateway router. AKA Data Center Interconnect (DCI)
The vRouter will exchange routes via MP-BGP and there is a setting in Contrail to create the Router-Target. The BGP family types vRouter supports is inet-vpn (or vpnv4) and evpn.
Overall the provisioning is fairly simple. There are a few things I would like "improved" in the product, such as being able to attach a policy from the networking overview "tab" instead of having to drill down into each network and doing it there. There could be a more excel feel to this view as you should be able to make modifications from this view using pulldowns or directly adding the ip subnets.
Also the manual process of creating VRFs on the Gateway router is a bit tedious. I'm investigating whether Openstack has the ability run a script that can make a netconf rpc call to the gateway router.
An alternative is to use slax and curl on a Juniper MX router to extract the details from the Contrail controller.