I originally posted this article on the RDO website.

The players

This document describes the architecture that results from a particular OpenStack configuration, specifically:

• Quantum networking using GRE tunnels;
• A dedicated network controller;
• A single instance running on a compute host

Much of the document will be relevant to other configurations, but details will vary based on your choice of layer 2 connectivity, number of running instances, and so forth.

The examples in this document were generated on a system with Quantum networking but will generally match what you see under Neutron as well, if you replace quantum by neutron in names. The OVS flow rules under Neutron are somewhat more complex and I will cover those in another post.