With libvirt, we can define different network types for our KVM guests, using the already familiar XML definition syntax and the
virt-install userspace tools. In this chapter, we are going to deploy three different network types, explore the network XML format, and see examples on how to define and manipulate virtual interfaces for the KVM instances.
To be able to connect the virtual machines to the host OS or to each other, we are going to use the Linux bridge and the Open vSwitch (OVS) daemons, userspace tools, and kernel modules. Both software bridging technologies are great at creating Software-defined Networking (SDN) of various complexity, in a consistent and easy-to-manipulate manner. The Linux bridge and OVS both act as a bridge/switch that the virtual interfaces of the KVM guests can connect to.
With all this in mind, let's start by learning more about the software bridges in Linux.