Neutron enables users to build routers that provide connectivity between networks created by users and external networks. In a reference implementation, the Neutron L3 agent provides IP routing and network address translation for virtual machine instances within the cloud by utilizing network namespaces to provide isolated routing instances. By creating networks and attaching them to routers, users can expose connected virtual machine instances and their applications to the internet.

Prior to the Juno release of OpenStack, users were limited to building standalone routers that acted as single points of failure in the network stack. Since the advent of distributed virtual routers in Juno and beyond, standalone routers are now referred to as legacy routers. While the preference may be to provide resiliency in the form of highly-available...