朴泊斋

1. sudo gvim /etc/network/interfaces: 
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual

auto br0
iface br0 inet dhcp
        bridge_ports eth0

2. sudo /etc/init.d/networking restart
3. install guest os
4. modify /etc/libvirt/qemu/guest_os_name.xml
    <interface type='bridge'>
      <mac address='your mac address'/>
      <source bridge='br0'/>
    </interface>
5. sudo virsh define guest_os_name.xml
6. start kvm again