Ever wondered about the underlying mechanism used by AHV hosts to facilitate network communications for themselves and hosted VMs across a network? This underlying mechanism is an open-source software platform called Open vSwitch which operates as a software-defined switch on each host.
This software-defined switch operates very similarly to a traditional layer-2 hardware switch in that it learns and maintains MAC addresses and makes frame-forwarding decisions based upon that information. However, it also can be considered much more scalable and extendable.
With AHV, each host maintains its own Open vSwitch instance and parameters are passed to these instances using an open-standard protocol called OpenFlow.