Learning OpenStack Networking - Third Edition

Routing traffic in the cloud

In a reference implementation, virtual routers created in Neutron exist as network namespaces that reside on nodes running the Neutron L3 agent service. A virtual router is often connected to a single external provider network and one or more project networks. The router interfaces connected to those networks can be identified as follows:

• qg: Gateway interface
• qr: Router interface

Neutron routers are responsible for providing inbound and outbound connectivity to and from project networks through the use of Network Address Translation, or NAT. The following diagram shows how a router namespace may be connected to multiple bridges in a Linux bridge-based implementation:

The preceding diagram demonstrates ...