Prior to the introduction of Neutron in the Folsom release of OpenStack, all network management was built in to the Nova API and was known as nova-network. Nova-network provided floating IP functionality, and network failure domains were limited to an individual compute node – something that was lacking in the early releases of Neutron. Nova-network has since been deprecated and most of its functionality has been implemented and improved upon in the latest releases of Neutron. In the last chapter, we looked at using VRRP to provide high-availability using active-standby routers. In this chapter, we will look at how distributed virtual routers borrow many concepts from the nova-network multi-host model to provide high-availability and smaller network failure domains while retaining support for many of the advanced networking features provided by Neutron.

Legacy routers, including standalone and active-standby, are compatible with multiple mechanism drivers, including the Linux bridge and Open vSwitch drivers. Distributed virtual routers, on the other hand, require Open vSwitch and are only supported by the Open vSwitch mechanism driver and agent. Other drivers and agents, such as those for OVN or OpenContrail, may provide similar distributed routing functionality, but are out of the scope of this book.