Learning OpenStack Networking - Third Edition

Using the L2 population driver

The L2 population driver was introduced in the Havana release of OpenStack alongside the ML2 plugin. It enables broadcast, multicast, and unicast traffic to scale on large overlay networks constructed by OpenStack.

The goal of the L2 population driver is to inhibit costly switch learning behaviors by pre-populating bridge forwarding and IP neighbor (ARP) tables on all hosts. Because Neutron is seen as a source of truth for the logical layout of networks and instances created by users, it can easily pre-populate forwarding tables consisting of MAC addresses and destination VTEPs with that information. The L2 population driver also implements an ARP proxy on each host, eliminating the need to broadcast ARP requests ...