Within Nova, the nova-network process manages VM network connectivity and related network capabilities (e.g., IP Address management, DHCP, L3 + NAT forwarding, VPN). Nova supports plugging in different implementation of ''managers'' for this network service, and Quantum takes advantage of this by creating a standard Quantum Manager that communicates with Quantum to allow Nova and Quantum to integrate.
To enable the Quantum Manager, your nova-network service must specify the following flag:
network_manager=nova.network.quantum.manager.QuantumManager
Nova defaults to connecting to Quantum on localhost using the standard port. The "quantum_connection_host" and "quantum_connection_port" flags can override these defaults.
With Quantum Manager, you can run only one instance of the nova-network process at a time. In particular, this means that a "multi_host" configuration where nova-network runs on each compute host is not supported. A common configuration is to run nova-network on a "nova controller" host along with nova-schedule, and have an active-passive high-availability strategy that restarts nova-network on another host if the main controller host fails.
