[libvirt] about open vswitch supporting？

[Laine Stump]

On 09/03/2012 06:41 AM, yue wang wrote:
>
>
>                     Hi:
>
>
>                     i used to use linux bridge and specify interfaces
>                     by 'Generic ethernet connection' mode,after
>                     reading this page：
>
>
>                     http://libvirt.org/formatdomain.html#elementsNICS
>

Actually, for a standard linux bridge, you should be using <interface
type='bridge'> rather than <interface type='ethernet'> ("generic
ethernet connection"):

  http://www.libvirt.org/formatdomain.html#elementsNICSBridge

type='ethernet' should only be used if there is some special setup that
can't be taken care of by the standard types; type='ethernet' requires
special permissions that aren't normally required, and "taints" the
guest - it's considered to be unsupported.

>
>
>                     i am not sure if i need to change to another
>                     mode(eg:'virtual network') to specify interfaces
>                     when switching linux bridge to open vswitch?
>
>           any suggestions?
>

As long as your libvirt version is new enough (0.9.11 or newer), you can
continue to use <interface type='bridge'> (as you should have previously
been), and add a <virtualport type='openvswitch'> element to the
interface definition. For example, if you were previously using a linux
bridge at br0, you would have have used:

   <interface type='bridge'>
     <source bridge='br0'/>
     ...
   </interface>

and if you switch to using an Open vSwitch bridge named ovsbr0, you
would change that to:

   <interface type='bridge'>
     <source bridge='ovsbr0'/>
     <virtualport type='openvswitch'/>
     ...
   </interface>

(you will notice that after you've edited you interface definition like
this, libvirt will automatically add a "<parameters interfaceid="[some
uuid string]"/> to the <virtualport> element. This is so that the
guest's interface can be known by a stable id that won't change as the
guest is stopped/restarted/migrated.)


If your libvirt is older than 0.9.11,you will need to either use the
Open vSwitch compatibility library to make your Open vSwitch bridge
appear to be a standard Linux host bridge, *or* you wil need to use
<interface type='ethernet'> along with an ifup script. I would
*strongly* recommend that you upgrade to 0.9.11+ if at all possible.