(1)brctl show
(2)virsh net-list
(3)virsh net-destroy default
Network default destroyed
(4)virsh net-undefine default
(5)service libvirtd restart
redhat7:systemctl restart libvirtd.service
重新用命令：virsh net-list和brctl show查看，发现已经没有了。
★卸载虚拟网卡
rpm -q libvirt*
yum remove libvirt-daemon 移除libvirt-daemon程序包
