oVirt: How to Create an Internal Network

By internal network, I mean a network that does not correspond to a physical NIC. It exists purely to allow VMs to communicate with each other.

On the oVirt Node

With that said, let’s begin. oVirt requires that all networks, even internal ones, correspond to a NIC. So step one is to make the host think that it has an extra NIC. We can do this with a dummy interface:

install dummy /usr/sbin/modprobe --ignore-install dummy; /usr/sbin/ip link set name dummy0 dev dummy

To have this automatically happen, those lines should also be added to /etc/modprobe.d/dummy.conf.

Also, run the following to make sure the dummy module is added on reboot:

echo "dummy" > /etc/modules-load.d/dummy.conf

Finally, make the network script for the interface. This should be in /etc/sysconfig/network-scripts/ifcfg-dummy0:

DEVICE=dummy0
BRIDGE=$Internal-network-name
ONBOOT=yes
MTU=1500
DEFROUTE=no
NM_CONTROLLED=no
IPV6INIT=no

Replacing $Internal-network-name with the name of the network you made on the oVirt web interface.

With all that done, when assigning networks to NICs in oVirt, you should now see dummy_1 as an option. Do be warned that this network will only exist on this host.