Xen domU can’t have access to outside dom0

I have successfully installed xen and run a domU on a debian squeeze.

I have followed step by step this tutorial here. I can log in my domU by SSH but from the domU I can't connect to anything but the dom0 itself.

Can anyone help me to enable network from my domU to the ouside?

Here is my xend-config.sxp file:

    root@dom0:/etc/xen# grep -Evn "^#|^$" xend-config.sxp 
    145:(network-script 'network-bridge')
    176:(vif-script vif-bridge)
    193:(dom0-min-mem 196)
    197:(enable-dom0-ballooning yes)
    207:(total_available_memory 0) 
    211:(dom0-cpus 0)
    226:(vncpasswd '')
    root@dom0:/etc/xen#

Here is my domU.cfg file:

root@dom0:/etc/xen# cat domU.cfg 
#  Kernel + memory size
kernel      = '/boot/vmlinuz-2.6.32-5-xen-686'
ramdisk     = '/boot/initrd.img-2.6.32-5-xen-686'

vcpus       = '1'
memory      = '128'

#  Disk device(s).
root        = '/dev/xvda2 ro'
disk        = [
      'file:/data/xen/domains/domU.telergos.net/disk.img,xvda2,w',
      'file:/data/xen/domains/domU.telergos.net/swap.img,xvda1,w',
          ]

#  Physical volumes

#  Hostname
name        = 'namaka-vm.telergos.net'

#  Networking
vif         = [ 'ip=172.23.154.105,mac=00:16:3E:04:8E:7A']
#  Behaviour
on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'[/CODE]

I don't have any xenbr when I run ifconfig:
only eth0, peth0, lo and vif1.0

When I run tshark -f '!port 22' I can see ARP requests when I try to ping others hosts than my dom0 but no answer. It looks like these ARP packets ar stuck in the dom0 host.

Here is iptables -L output:

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED PHYSDEV match --physdev-out vif1.0 
ACCEPT     udp  --  anywhere             anywhere            PHYSDEV match --physdev-in vif1.0 udp spt:bootpc dpt:bootps 
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED PHYSDEV match --physdev-out vif1.0 
ACCEPT     all  --  domU  anywhere            PHYSDEV match --physdev-in vif1.0[/CODE]

I am ways too newbie to fully understand this configuration, but it looks like it is applied at boot time.

I have thought that dom0 may not know what to do with domU packets, but do0 is supposed to act as a bridge! So, it should simply relay these packets on its eth0 interface, letting my switch relay them on the others hosts…

Thank you for your time and help!