Re: [Xen-users] xen networking problem

[Big Strong <fangtuo90@xxxxxxxxx>]

Thanks very much for the clear explanation.

2016-08-14 11:54 GMT+08:00 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@rz-online.de
                         http://rz-home.de/mhaertel

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