oVirt Blog

oVirt Software Defined Networking, The OVN Network Provider

oVirt offers not only its own internal networking, but also an API for external network providers. This API enables using external network management software inside environments managed by oVirt and takes advantage of their extended capabilities.
One of such solutions is OVN: Open Virtual Network. OVN is an OVS (Open vSwitch) extension that brings Software Defined Networking to OVS.

OVN enables support for virtual networks abstraction by adding native OVS support for virtual L2 and L3 overlays.
This allows the user to create as many VM networks as required, without troubling the adminstrator with vlan requests or infrastructure changes.


Modifying oVirt-Generated ifcfg Files

oVirt is using a bridge based setup to configure networks on the managed hosts. The setup process is done by generating and maintaining network interface configuration files (ifcfg file), which define the network devices used by oVirt.
Should any changes be done to these files by an outside party, oVirt will try to restore them to the desired state, to keep the network configuration intact.
There are however situations in which the user want to intentionally introduce permanent changes into some of these files, and prohibit oVirt from overwritting them. In order to do so, VDSM hook script can be used.