virtio driver: seeing all packets. Is this expected?

[rschmied]

I'm using VB 4.0 on Linux Lucid 64 and Mac OS X 10.6 with various guests. Since switching to VB 4.0 I've changed the NIC in my Linux guests to the virtio NIC driver. Now I'm observing that all my Linux guests see all traffic from the host NIC and not only the traffic that is addressed to their MAC address (from a networking perspective it looks as if the guest is connected via a hub to the host resulting in seeing all packets. Where as in a switched environment it would only see the packets that are addressed to the guest or broad / multicast packets). This is especially painful as the host boots from iSCSI and some of the VDI images of the guests reside on NFS shares... IOW, I'm seeing a pretty high interrupt load on my guests resulting from traffic on the net that should not be seen by the guest in the first place.

• is this expected? or a bug?
• On the Linux host, I could setup a bridge and attach a tap interface to the bridge, connecting the guest to the tap interface, that would solve the problem but would add additional processing overhead on the host... is this recommended?
• have others experienced similar behavior?

Thanks,
-ralph

[fixedwheel]

i have no experience in this, but with your given precondition i would go that way:

connecting the guest to the tap interface, that would solve the problem

[rschmied]

Thanks for replying... And I would agree that it removes the symptoms but not the problem (also not speaking of the additional performance overhead which was the reason I went down the virtio path). Especially since there's no such thing (brctl, bridging of interfaces) on a Mac and I'm also not sure if that could be easily done on Windows platforms.