Re: [Xen-users] xen networking problem

["Manfred Haertel, DB3HM" <Manfred.Haertel@xxxxxxxxxxxx>]

Sarah Newman schrieb:
> On 08/13/2016 05:57 AM, fangtuo90 wrote:
> > I'm using openvswitch as the bridge. And for the VM dom1, two interfaces are 
> > created, vif1.0 and vif1.0-emu. Both have bytes received and transmited, but 
> > not equal. Which one represents the traffic of dom1? It is needed to be 
> > classified to adjust the route of the VM based on it's ports, or dump traffics 
> > for analysis.
> Both.
>
> https://wiki.xen.org/wiki/Xen_Networking#Emulated_Network_Devices
The VM *could* use both vif devices, but typically it decides for one of 
them and most often this is the paravirtualized one. E.g. the Linux 
kernel, whenn running in a Xen VM, does so.
However, since the Xen DOM0 does not know for which interface the VM 
would decide, it typically connects *both* Devices to the virtual 
bridge. This does not harm, if one of them is not used.
Because the virtual bridge has to flood broadcast packets to all its 
ports, typically you can see quite a few *transmitted* packets also on 
the unused device. On the other hand, the number of *received* packets 
should be 0, and it is on my Xen DOM0 (just checked).
--
Manfred Härtel, DB3HM    mailto:Manfred.Haertel@xxxxxxxxxxxx
                         http://rz-home.de/mhaertel

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