No guest network with KVM using vmbuilder

[Walter Souto]

Hi, I hope I'm not asking something dummy, anyway...

So, I'd use vmbuilder to create a VM like this:

sudo vmbuilder kvm ubuntu \
--suite lucid --flavour virtual --arch amd64 -o -v \
--libvirt qemu:///system \
--cpus 1 --mem 256 \
--rootsize 8192 --swapsize 2048 \
--hostname vm101 \
--ip 10.0.3.11 --mask 255.255.252.0 --net 10.0.0.0 --bcast 10.0.3.255 \
--gw 10.0.3.254 --dns 10.0.3.254 --bridge br0 \
--user sysadmin --name SysAdmin --pass 656667 \
--addpkg acpid \
--addpkg openssh-server \
--mirror http://ironman:9999/ubuntu \
--raw /dev/vgvm/lvm01

The host (lucid) has bridge br0 configured and forwarding with
10.0.0.1 / 255.255.252.0. The configurations seems to be ok:

<domain type='kvm'>
  <name>vm101</name>
  <uuid>43cf30ee-1d29-2c34-ebda-f16b9c2472bc</uuid>
  <memory>262144</memory>
  <currentMemory>262144</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64' machine='pc-0.12'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <source file='/dev/vgvm/lvm01'/>
      <target dev='hda' bus='ide'/>
    </disk>
    <interface type='bridge'>
      <mac address='52:54:00:19:fd:7c'/>
      <source bridge='br0'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
    </interface>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes' listen='127.0.0.1'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
    </video>
  </devices>
  <seclabel type='dynamic' model='apparmor'/>
</domain>

I can't connect to the machine via SSH with the given IP. I can't ping
too. I have no clue about what can be wrong.  I did some research on
this list but no lucky...

TIA,
--
Walter.