[libvirt] how do I stop libvirt futzing with my network configuration?

Daniel P. Berrange berrange at redhat.com
Mon Nov 30 09:57:43 UTC 2009

On Sat, Nov 28, 2009 at 10:06:16PM +0000, Nix wrote:
> On 28 Nov 2009, Ian Woodstock spake thusly:
> > I've been running with this configuration for many months on dozens of hosts.
> >
> > - Created a bridge (the old fashion way) in /etc/sysconfig/network-scripts
> > Bridge called br0 with one device eth1.
> >
> > - Created a VM in virt manager (or edit existing)
> > Picked "Shared Physical Device"  Device "eth1 (Bridge br0)"  in the GUI.
> That's the mystery. I did it (directly via brctl, as it happens, 'cos I'm
> making several with particular properties and want to enforce them):
> spindle:/etc/libvirt/qemu# brctl show
> bridge name     bridge id               STP enabled     interfaces
> linux-net               8000.06eb4e4985df       no              dummy0
> [...]
> 52: linux-net: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
>     link/ether 06:eb:4e:49:85:df brd ff:ff:ff:ff:ff:ff
>     inet scope global linux-net
> (hm, the state UNKNOWN is sort of bizarre. It's up...)
> (dummy0 is a member of this bridge because I've previously noted that a
> bridge with no members at all isn't picked up by the GUI).
> It appears in the GUI, all right: as 'host device linux-net (not bridged)',
> greyed out and unselectable. Calling a bridge 'not bridged' is more than
> slightly bizarre.

What's confusing it here is that you've not connected a real physical
network interface to the bridge - it is expecting to find a ethernet
device enslaved, and instead finds 'dummy0'.

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