Re: [Xen-users] Alternative to network-nat on Debian Squeeze with XEN4?

["Fajar A. Nugraha" <list@xxxxxxxxx>]

On Mon, Jun 20, 2011 at 11:47 AM, Andrew Sorensen <andrewx192@xxxxxxxxx> wrote:
> On Mon, 2011-06-20 at 11:24 +0700, Fajar A. Nugraha wrote:
>> On Mon, Jun 20, 2011 at 11:11 AM, Andrew Sorensen <andrewx192@xxxxxxxxx> 
>> wrote:
>> >>
>> >> Todd: Is this the same one used by libvirt with virbr0? Using
>> >> something common would be nice, as it means NAT-networking can be
>> >> treated the same way as bridge networking from Xen's perspective.
>> >>
>> >> Andrew: try installing virt-manager (or perhaps libvirt-bin is
>> >> enough). It should create a bridge called virbr0, which you can use on
>> >> domU config file (add "bridge" section to vif line).
>> >>
>> >> --
>> >> Fajar
>>
>> > I already have bridged networking working, but would like to add NAT to my
>> > setup.. I'd rather stay away from libvirt as it has caused problems in the
>> > past. I don't see the need to have libvirt to accomplish my requirements.
>>
>> libvirt simply makes it easier to setup virbr0. If you don't use
>> virt-manager/virt-install, then basically it's all libvirt does:
>> create virtbr0.
>>
>> If you're familiar enough with manual bridge and NAT setup, you could
>> just create it manually, which would involve:
>> - create a bridge with is not connected to any physical host
>> - create NAT MASQUARADE rule for any traffic coming from that bridge
>> - (optional) run dnsmasq to provide DHCP and DNS
>>
>> With that kind of setup (either manual or created by libvirt) you can
>> simply use bridge networking in Xen as usual, and it doesn't matter
>> whether your uplink is already bridged or not. And the same bridge+NAT
>> setup can be used for other virtualization setup as well (For example,
>> I'm using libvirt to create a bridge on my Virtualbox setup, which
>> Virtulbox uses later as bridged networking)
>>
> That was what I was trying to do. If you visit
> http://wiki.qemu.org/Documentation/Networking/NAT and take a look at
> that script at the bottom, it creates a bridged interface and takes in a
> a parameter to add to the NAT bridge. I'm not sure what I would need to
> modify in that script to create the NAT MASQUARADE rule.

... and what I've been trying to say is that you don't have to use
that script. Not if it gives you more trouble.

Instead, I suggest you split it into two separate process:
(1) Creation of the bridge with NAT support
(2) Adding domU's vif to that bridge

For (1) Can be done with either libvirt or setup manually.
For (2), you can simply use Xen's existing bridge script. No need to
create additional network script.

-- 
Fajar

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