Using the HTTP server via TAP

mx at ...19... mx at ...19...
Wed Jun 2 14:23:39 CEST 2010

Hi Peter,

Peter Nguyen <petern at ...34...> hat am 2. Juni 2010 um 13:47

> Hi Sven,
> > I'm not sure if I've got your setup right or not.
> >
> > You have a host operating system (guess linux) with two qemu 
> > instances, one running Windows XP and the other running genode with 
> > the webserver.
> >
> > Your host system also runs a dhcp server which assigns the same ip 
> > address to both qemu instances.
> >
> I have this exact setup, where the host operating system is Ubuntu.
> > This assignment could be caused by the fact that both qemu instances 
> > have the same mac address.
> >
> > The 10.02 release notes state that the nic driver "fakes an ethernet 
> > NIC with the MAC address 02-00-00-00-00-01". Where could that MAC 
> > address come from? The driver obtains it from qemu in dde_tx_handler:
> >
> > dde_linux26_net_get_mac_addr(1, (unsigned char*)_mac_addr.addr);
> >
> >
> > This schould be exactly that MAC address you shoud have configured 
> > when starting up qemu (did you?):
> >
> > This could look like "-net nic,model=pcnet,macaddr=00:81:71:61:51:41"
> >
> > Perhaps you forgot this step?
> >
> So you're saying that when i run the web server, I need to explicitly 
> state the mac address as stated above? If so, what about the XP 
> machine. I've tried setting the mac address to something different, 
> but so far it hasn't worked. Let me try this again.
This is just an example taken from a different setup I was working on a few
months ago. Of course, you're free to choose any MAC address you like (make sure
that the first byte is an even number, otherwise, your packets might be
I don't know exactly where qemu takes its virtual MAC address from when you omit
it in the configuration, therefore it could be helpful to make them distinct in
any case.
My suggestion is nothing more than an uncertain idea, and I would always suggest
to trace the whole packet flows with wireshark which would show quite obviously
which interfaces uses which MAC address and which IP address has been assigned
to it.

> Thanks
> Peter
> ------------------------------------------------------------------------------
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Sven Fülster
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