KVM上创建VM，以及给VM建立子网

以下操作都是在ubuntu10.04系统下进行的。
1.vi /etc/libvirt/qemu/networks/qybr.xml
<network>
  <name>qybr10</name>
  <uuid>80eab63e-2b1e-4844-b237-0bb3288c39c3</uuid>
  <forward mode='nat'/>
  <bridge name='qybr10' stp='on' delay='0' />
  <ip address='10.10.10.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='10.10.10.2' end='10.10.10.254' />
    </dhcp>
  </ip>
</network>
2.virsh net-define /etc/libvirt/qemu/networks/qybr10.xml
  virsh net-autostart qybr10
  virsh net-start qybr10
3.vi /etc/libvirt/qemu/QianYuSrvZTE_IVR.xml
    <type arch='x86_64' machine='pc-0.12'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='localtime'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/QianYuSrvZTE_IVR.img'/>
   //指定img文件位置
      <target dev='hda' bus='ide'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/media/iso/zh-hans_windows_xp_professional_with_service_pack_3_x86_cd_vl_x14-74070.iso'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
    </disk>
    <interface type='bridge'>
      <mac address='52:54:00:70:a2:e4'/>
      <source bridge='qybr10'/>
    </interface>
    <console type='pty'>
      <target port='0'/>
    </console>
    <console type='pty'>
      <target port='0'/>
    </console>
    <input type='tablet' bus='usb'/>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
    </video>
  </devices>
</domain>
4. create a new VM:
virsh define /etc/libvirt/qemu/QianYuSrvZTE_IVR.xml
virsh start QianYuSrvZTE_IVR
5.port forwarding:  10180
      iptables -t nat -I PREROUTING -p tcp --dport 10180 -j DNAT --to-destination 10.10.10.xx:80
      iptables -I FORWARD -m state -d 10.10.10.0/24  --state NEW,RELATED,ESTABLISHED -j ACCEPT

注：子网建立完之后如何进行删除 virsh net-destroy /etc/libvirt/qemu/networks/xxx
                               virsh net-undefine /etc/libvirt/qemu/networks/ xxx