You must run the command that creates the network and the bridge using the br100 specified in the nova.conf file to create the network that the virtual machines use. This example shows the network range using 192.168.100.0/24 as the fixed range for our guest VMs, but you can substitute the range for the network you have available. We're labeling it with private in this case. nova-manage network create private --fixed_range_v4=192.168.100.0/24 --bridge_interface=br100 You can find out more about the nova-manage network create command with nova-manage network create -h.