The graphical interface installed according to the above document does not have virbr0. If you execute **yum group install "Server with GUI" -y according to other documents on the Internet, there will be a bridge appearing, and this bridge is nothing. Used, it will appear every time ifconfig, looks very awkward, execute the following command to delete
ip add list
yum install libvirt
virsh net-list
virsh net-destroy default
virsh net-undefine default
service libvirtd restart
virsh net-list
ip add list
yum remove libvirt