Like other OpenStack services, Networking enables you to run services across multiple physical devices. It is also possible to run all service daemons on a single physical host for evaluation purposes. Alternatively, you can run each service on a dedicated physical host and replicate certain services across multiple hosts for redundancy purposes. For more information, see the OpenStack Configuration Reference.
A standard architectural design includes a cloud controller
host, a network gateway host, and a number of hypervisors
for hosting virtual machines. The cloud controller and
network gateway can be on the same host. However, if
you expect VMs to send significant traffic to or from
the Internet, a dedicated network gateway host helps
avoid CPU contention between the neutron-l3-agent and
other OpenStack services that forward packets.
