Learning OpenStack Networking - Third Edition

Overlay networks

Neutron supports overlay networking technologies that provide network isolation at scale with little to no modification of the underlying physical infrastructure. To accomplish this, Neutron leverages L2-in-L3 overlay networking technologies such as GRE, VXLAN, and GENEVE. When configured accordingly, Neutron builds point-to-point tunnels between all network and compute nodes in the cloud using a predefined interface. These point-to-point tunnels create what is called a mesh network, where every host is connected to every other host. A cloud consisting of one combined controller and network node, and three compute nodes, would have a fully meshed overlay network that resembles figure 1.2:

Figure 1.2

Using the overlay network ...