[Qemu-devel] Networking possibilities

[Qemu-devel] Networking possibilities

[Ming-Ching Tiew]

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I would like to know if it is possible to run a few instances
of Qemu's ( ie a few guest OS'es ) and make them network 
with one another ? In each of the instance there maybe 
multiple network cards, I would like to be able to specify each 
network card to go to which tun device and then allow another 
instance to connect specifically to that particular tun device,
instead of only connected to the host OS.

That's tun/tap devices are used to connect multiple instances
of qemu together or with the host OS.

Bottomline I would like to be able to set up a farm of guest OS's
which could perform internetworking among each other. This is
extremely useful for testing/developing networking software. 
Is it possible ?

Cheers

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Re: [Qemu-devel] Networking possibilities

[Doug Stanley]

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I believe this is exactly what the vde_switch software
was meant for.
Google for vde_switch...or check out
http://vde.sourceforge.net/

Doug

Ming-Ching Tiew wrote:
>  
> I would like to know if it is possible to run a few instances
> of Qemu's ( ie a few guest OS'es ) and make them network
> with one another ? In each of the instance there maybe
> multiple network cards, I would like to be able to specify each 
> network card to go to which tun device and then allow another
> instance to connect specifically to that particular tun device,
> instead of only connected to the host OS.
>  
> That's tun/tap devices are used to connect multiple instances
> of qemu together or with the host OS.
>  
> Bottomline I would like to be able to set up a farm of guest OS's
> which could perform internetworking among each other. This is
> extremely useful for testing/developing networking software.
> Is it possible ?
>  
> Cheers
> 
> 
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> 
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> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel

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Re: [Qemu-devel] Networking possibilities

[Felipe Sanchez]

On Mon, 27 Dec 2004, Ming-Ching Tiew wrote:
> Bottomline I would like to be able to set up a farm of guest OS's
> which could perform internetworking among each other. This is
> extremely useful for testing/developing networking software.
> Is it possible ?

It's certainly possible, I have such a setup in a couple of servers. All
you have to do is to specify a network setup script with the "-n" command
line option and set the appropriate IP addresses and routes. Feel free to
ask me about specific details.

The part about linking a specific tun device to a specific network
interface in the guest OS sounds a bit trickier though. Maybe the patch
posted a while ago that allows to tell qemu the name of preconfigured tun
devices might be helpful.

Re: [Qemu-devel] Networking possibilities

[Tim]

> I would like to know if it is possible to run a few instances
> of Qemu's ( ie a few guest OS'es ) and make them network 
> with one another ? In each of the instance there maybe 
> multiple network cards, I would like to be able to specify each 
> network card to go to which tun device and then allow another 
> instance to connect specifically to that particular tun device,
> instead of only connected to the host OS.
> 
> That's tun/tap devices are used to connect multiple instances
> of qemu together or with the host OS.
> 
> Bottomline I would like to be able to set up a farm of guest OS's
> which could perform internetworking among each other. This is
> extremely useful for testing/developing networking software. 
> Is it possible ?


One possible way to do this would be to spawn all of your Qemu
instances, each with their own TUN interface, then bridge the TUN
interfaces together on the (linux) host.  Linux bridging code comes
standard with 2.6 kernels now (i believe), and I have used it before to
bridge a Qemu TUN interface with a physical interface in the host
before.  I haven't tried putting together multiple TUN interfaces before
though. 

There are several references online for how to do Linux bridging.  If
you can't find them through google, I can dig up a link.

HTH,
tim

Re: [Qemu-devel] Networking possibilities

[Jim C. Brown]

On Mon, Dec 27, 2004 at 08:26:56PM +0800, Ming-Ching Tiew wrote:
> 
> I would like to know if it is possible to run a few instances
> of Qemu's ( ie a few guest OS'es ) and make them network 
> with one another ? In each of the instance there maybe 
> multiple network cards, I would like to be able to specify each 
> network card to go to which tun device and then allow another 
> instance to connect specifically to that particular tun device,
> instead of only connected to the host OS.

You don't need multiple tuntap devices in the guest, you only need one.

> 
> That's tun/tap devices are used to connect multiple instances
> of qemu together or with the host OS.

There are two ways I can think of to do this.

The easy way is to use VDE (vde.sourceforge.net), which allows you to share a
single tuntap device amoung all qemu instances. (Or, if you don't have root
permissions, it can even emulate a tuntap device for you). The VDE HOWTO should
give the basics on how to do this.

The hard way is to set up each qemu instance normally, and then connect them
together thru the host, either with bridging or iptable tricks.

> 
> Bottomline I would like to be able to set up a farm of guest OS's
> which could perform internetworking among each other. This is
> extremely useful for testing/developing networking software. 
> Is it possible ?

Yes.

> 
> Cheers


-- 
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.