PXE boot a virtual machine with NAT connection to the host

If you have a notebook and you want to quickly deploy new virtual machines for testing, PXE boot is your friend.

On notebooks people are usally not using a bridged network but NAT instead. The DHCP server on the host that is managed by Libvirt needs to configured with the TFTP server and the boot file.

On my “mobile lab”, I’ve installed a virtual machine with a Redhat Satellite 5 where the other VMs get its content from. PXE boot files are managed by the bundled Cobbler Server.

To do so, edit the XML file of the default network (or any other NAT network):

notebook-hv:~# virsh net-edit default

Add the red marked line to the file. Replace 192.168.122.122 with the actual IP address of your PXE/TFTP server.

<network>
  <name>default</name>
  <uuid>d54b7049-254b-46b0-b434-db2a1481cbd3</uuid>
  <forward mode='nat'/>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:96:21:b5'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.2' end='192.168.122.254'/>
      <bootp file='pxelinux.0' server='192.168.122.122'/>
    </dhcp>
  </ip>
</network>

And save it. The changes are with immediate effect, happy PXE-booting 🙂