networking with qemu

JackDog · Posted: Mon Nov 15, 2004 3:23 pm Post subject: networking with qemu

Does anyone know the best way to setup qemu to simply use a virtual ehternet device instead of piggy backing on my primary eth0? I would like to write a script that would launch qemu in such a way that it uses a virtual eth device so that it can actually be "on the network" rather than firewalled on a private subnet...

bravecobra · Posted: Thu Feb 24, 2005 3:07 pm Post subject:

I've tried this, but I can't seem to get it working
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Lejban · n00b Joined: 12 Dec 2003 Posts: 53 Location: Sweden

bravecobra · Posted: Fri Feb 25, 2005 1:31 am Post subject:

Did some research today and placed my findings in my blog: http://blog.bravecobra.com/index.php/linux/2005/02/25/emulating_an_os_with_qemu
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transienteagle · Apprentice Joined: 24 Dec 2003 Posts: 190 Location: UK

bravecobra,

good work and many thanks. This had me foxed for quite a while. To get it all working (internet / access to host and host lan etc) I set up the windows XP guest on a different subnet.

My actual configuration turned out to be; Host ip address 10.0.0.1, DNS server 10.0.0.138, host tun device 11.0.0.8;
guest ip address 11.0.0.5 default gateway 11.0.0.8 dns server 10.0.0.138;

my script to get windows XP working within qemu is

ExElNeT · n00b Joined: 11 Feb 2003 Posts: 37

Is there a way to get a all lan clients and vms in the same subnet? I have 2 vms running on one machine and they cant connect to eachother. A connection to the DNS server and the gateway is possible.

My goal is to create a small network using vms.

ooky · n00b Joined: 25 Oct 2004 Posts: 35

I had the same problem.

https://forums.gentoo.org/viewtopic-p-2236102.html#2236102

fourhead · Posted: Sun Sep 11, 2005 3:52 pm Post subject:

@transienteagle

First, thanks for your how-to, it helped me a lot, but I'm still not 100% where I want to be. I have TWO qemu instances that I want to communicate with each other. Now with your how-to I was able to do the following:

Host: eth0 192.168.1.10, tun0 192.168.1.30
qemu-1: eth0 192.168.1.40, gw 192.168.1.30
qemu-2: eth0 192.168.1.50, gw 192.168.1.30

On the host, route looks like this:

Redeeman · l33t Joined: 25 Sep 2003 Posts: 958 Location: Portugal

why not just use the --user-net thing, then you dont need a tun/tap device

fourhead · Posted: Sun Sep 11, 2005 5:42 pm Post subject:

OK, I tried that, I started both qemu's with -user-net. Both vms then get the IP 10.0.2.15, the DHCP server and router that qemu provides is 10.0.2.2. I can reach the Internet with both vms, but of course I can't ping between them. So I set the second vm to a static config with 10.0.2.16 and left all other settings as they are ... but nothing happend. I still can't ping from one vm to the other.

What I tried with tun and bridging was the following:

Start the first qemu on tun0, tun0 has 192.168.1.30. Start the second qemu on tun1 with 192.168.1.31. The internal IP's that the guest OS has 192.168.1.40 and .50 respectively. I now thought I could create a bridge br0

brctl addbr br0

and then connect tun0 and tun1 together:

brctl addif tun0
brctl addif tun1
ifconfig br0 up

But the both VMs still can't ping each other. I'm pulling my hair out because of this, I'm trying the whole day now. Is there any easy iptables rule or bridge setup so that a ping that goes from qemu1->tun0->tun1->qemu2. Or, as I first tried it, use VDE, connect both qemus to the same tun device which also didn't work. I always have full networking, EXCEPT between the two virtual machines....

Any help on this would be very appreciated, I have to get this to work somehow!!

Tom

mel_82 · Posted: Wed Feb 15, 2006 6:02 pm Post subject:

I think that ping between VM was implemented in QEMU from 0.8..

Is it true?
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