Jan Luebbe <jlue...@lasnet.de> writes:
> Hi!
>
> On Mon, 2009-10-19 at 16:23 +0200, Goswin von Brederlow wrote:
>> sudo kvm -m 256 -drive
>> file=/scratch/ramdisk/build/build/hda.img,if=ide,boot=on -drive
>> file=/scratch/ramdisk/build/build/hdb.img,if=ide,boot=off -net
>> nic,model=e1000,macaddr=54:52:00:00:42:12 -net tap -net
>> nic,model=e1000,macaddr=54:52:00:00:42:13 -net tap -smp 1
>> -kernel
>> /scratch/ramdisk/build/build/chroot-amd64/boot/vmlinuz-2.6.27.34-1-ql-beowulf
>> -append root=/dev/ram0 rw ramdisk_size=97872 console=ttyS0,115200 quiet
>> --initrd /scratch/ramdisk/build/build/image-beobox-amd64-7.0.0-0.gz
>> -nographic
>>
>> and the /etc/kvm/kvm-ifup script adds both devices to a bridge:
>
> The is an effect of how qemu's internal networking is designed.
>
> You defined 2 nics and *2 tap devices* on the same qemu-internal vlan.
> Bridging these devices together creates a loop.
>
> If you just want two devices in the same physical lan use '-net tap'
> only once. This will connect the two nics to the same tap device.
>
> You only need explicit vlans if you want to connect them to different
> bridges on the host.
>
> I don't think this is RC, maybe qemu should warn if more than one tap
> device is used on the same internal vlan.
>
> Jan
Definetly warn if not automatically put them in different vlans by
default. This behaviour is totaly unexpected. I created 2 tap devices
for a reason and kvm just merged them again. They were intended for
different bridges but the default kvm-ifup script put them into the
same bridge.
I can't think of any use case of having 2 tap devices in the same vlan
so the default should be changed to something less dangerous.
MfG
Goswin
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