[libvirt-users] Network without forward mode

[Laine Stump]

On 07/25/2016 02:49 AM, Vincent Bernat wrote:
>   ❦ 25 juillet 2016 08:44 CEST, Martin Kletzander <mkletzan at redhat.com> :
>
>>>> "Just a vnet interface, no bridge" means you want no network.  Where
>>>> should the vnet be connected?
>>> The host is able to handle the routing. It seems I could just declare an
>>> interface of type "ethernet" instead of "network" to get the effect I
>>> want.
>> I'm sorry, but I have no idea what is the end result you are trying to
>> achieve.  Could you describe what are your trying to set up without
>> libvirt technicalities?
> I have a process watching libvirt event to add a route like "ip route
> add 192.0.2.147/32 dev vnet18" once the VM is spawned. The host is then
> responsible for any routing to/from the VM. I don't want the VM to be
> part of a bridge.


Note that once libvirt 2.1.0 is released (just entered freeze 
yesterday), you will be able to specify the host-side IP address for the 
tap device, as well as any routes to add to the host, right within the 
<interface> element, e.g.:

    <interface type='ethernet'>
       <source/>
         <ip address='192.1.2.147' prefix='32'/>
         <route family='ipv4' address='192.0.2.147' prefix='32' 
gateway='192.1.2.147'/>
       <source/>
       ...
     </interface>


This will avoid the need to watch a libvirt event.


(it's interesting that you're apparently adding a route to the tap 
device without assigning an IP address to it. I'd never tried that, and 
didn't realize it would work.)