libvirt users - Mar 2016 - Re: Convincing libvirt to create a bridge device?

I was hoping that I could delegate creation of bridge devices to
libvirt for address-less bridges, in order to not have to deal with
the various ways distributions handle persistent network
configuration, but while this creates a libvirt network...

  <network>
    <name>provision</name>
    <forward mode='bridge'/>
    <bridge name='brprov'/>
  </network>

...it doesn't actually create the bridge.  Configuring the bridge
using either <forward mode="route"/> or <forward
mode="nat"/> *will*
create the bridge device, but both of these require assigning an
address to the bridge which means I have to suddenly worry about
IPAM and conflicts with local networks.

I look at the various interface-related commands, and there is an
"iface-bridge" command but this requires a physical interface.

Is there any way to convince libvirt to create the bridge device for a
<forward mode='bridge'/> network?

-- 
Lars Kellogg-Stedman <lars@redhat.com> | larsks @
{freenode,twitter,github}
Cloud Engineering / OpenStack          | http://blog.oddbit.com/

On 03/06/2016 03:21 PM, Lars Kellogg-Stedman wrote:
> I was hoping that I could delegate creation of bridge devices to
> libvirt for address-less bridges, in order to not have to deal with
> the various ways distributions handle persistent network
> configuration, but while this creates a libvirt network...
>
>    <network>
>      <name>provision</name>
>      <forward mode='bridge'/>
>      <bridge name='brprov'/>
>    </network>
>
> ...it doesn't actually create the bridge.  Configuring the bridge
> using either <forward mode="route"/> or <forward
mode="nat"/> *will*
> create the bridge device, but both of these require assigning an
> address to the bridge which means I have to suddenly worry about
> IPAM and conflicts with local networks.
Remove the <forward mode='bridge'/> line from your config above
and it
should do what you want - libvirt will create the bridge, but won't 
assign any IP address to it (nor will it attach it to any physical device).

On Sun, Mar 06, 2016 at 07:59:38PM -0500, Laine Stump
wrote:
> >configuration, but while this creates a libvirt network...
> >
> >   <network>
> >     <name>provision</name>
> >     <forward mode='bridge'/>
> >     <bridge name='brprov'/>
> >   </network>
> >
> >...it doesn't actually create the bridge...
> 
> Remove the <forward mode='bridge'/> line from your config
above and it
> should do what you want - libvirt will create the bridge, but won't
assign
> any IP address to it (nor will it attach it to any physical device).
Wow, that totally works, and makes my life much simpler.  Thanks!

-- 
Lars Kellogg-Stedman <lars@redhat.com> | larsks @
{freenode,twitter,github}
Cloud Engineering / OpenStack          | http://blog.oddbit.com/