The basics of routing in Neutron

If you recall from the previous chapter, users can create and manage networks known as tenant networks within their respective project without any knowledge of the underlying infrastructure. By default, instances connected to tenant networks are isolated from other networks and are unable to access external resources such as the Internet. Neutron provides connectivity to instances in tenant networks by way of virtual routers.

Network namespaces

In a reference implementation, virtual routers created in Neutron are implemented as network namespaces that reside on nodes running the Neutron L3 agent service. Network namespaces are similar in function to Virtual Routing and Forwarding (VRF) domains, where multiple instances of a routing table exist to provide complete network segregation in a single device. The use of network namespaces allows Neutron to support overlapping subnets across networks. In Linux, network namespaces can be managed using the ip netns...