openstack-manuals/doc/image-guide/source/net-running.rst

Verify the libvirt default network is running

Before starting a virtual machine with libvirt, verify that the libvirt default network has started. This network must be active for your virtual machine to be able to connect out to the network. Starting this network will create a Linux bridge (usually called virbr0), iptables rules, and a dnsmasq process that will serve as a DHCP server.

To verify that the libvirt default network is enabled, use the virsh net-list command and verify that the default network is active:

# virsh net-list
Name                 State      Autostart
-----------------------------------------
default              active     yes

If the network is not active, start it by doing:

# virsh net-start default