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[Xen-users] NAT problem

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Subject: [Xen-users] NAT problem
From: Julien Croquant <julien_croquant@xxxxxxxxxx>
Date: Tue, 11 Sep 2007 16:09:22 +0000
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I'm fresh new to Xen and I have a problem to use NAT.
I searched into this mailling-list and google but failed to find anything helpfull. The wiki at xensource have documentations, but nothing specific to NAT.

I use a test computer with Intel Core 2 Duo. A fresh Debian Etch install and Xen 3.0.3 from apt-get.
Everything is ok when I use bridge mode. My virtual machines work well and the network is ok. The /etc/xen/xend-config.spx is the original ones and do not need to be edited. I only have to create the config files for each virtual machines.

But when I try to use NAT this is another story.

What I do :
I comment (network-script network-bridge) and (vif-script vif-bridge) into /etc/xen/xend-config.spx
and I uncomment (network-script network-nat) et (vif-script vif-nat). Dummy and route lines are commented.

I then reboot to be sure everything is ok.
"brctl show" gives me nothing. Seems right.
"ifconfig -a" gives me only "eth0" and "lo" and "sit0". I don't know if this is correct.

I then modify the config file for a virtual machine :
bridge mode    vif = [ 'type=ioemu, bridge=xenbr0' ]
NAT mode   vif = [ 'ip=' ]

I then boot the virtual machine and... no NIC into the virtual machine. I use Windows XP as guest. If I restart in bridge mode, the NIC is here (RealTek 8139). When I try in NAT mode, no NIC.
"ifconfig -a" gives me "eth0" and "lo" and "sit0" and "vif2.0" on the host.
The vif2.0 have IP = (instead of

I'm sure I'm wrong somewhere, but I lack experience to know where. Maybe it is not fully automatic and I have to issue some commands. All I found about that are complex setup for very specific needs. Nothing about "just a NAT".

Someone have a hint or a link ? For example config files for Windows+NAT.

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