Re: [Xen-users] dom0 networking problem

[Jens Fiedler <jens.fiedler@xxxxxxxxxxxxxxxxxxx>]

Jens Fiedler wrote:

> John Smith wrote:
>
> > > ARP response. The ARP response is then sent over the network (one 
> > > single
> > > switch),
> > > passes the switch (checked using a hub after it), but does not show up
> > > in the
> > > Cheers,
> > > -Jens
> > Jens,
> >
> > it smells like a switch with autolearning.
> > I would try it with a hub _in stead_ of the switch.
> >
> > Sincerely,
> >
> > Jan.
> Hi,
>
> The ARP response passes the switch, the hub was placed behind the 
> switch in order to check
> wheter the switch drops the ARP response. It does not, I can see the 
> ARP responses using a
> 3rd machine (sniffer in the fig.) connected to that hub. So the switch 
> is not the point of
> failure.
>
>    <---------------------ARP request----------------
>    ----------------------ARP response---->
> +-------+                                     +-------------+
> |target |     +--------+       +-----+        | xen machine |
> |machine|-----| switch |-------| hub |--------|peth0        |
> +-------|     +--------+       +-----+        +-------------+
>                                  |
>                              +--------+
>                              | sniffer|
>                              +--------+
>
> Additionally, when I look at the packet counters using 'ifconfig', the 
> counters for TX and
> RX go up, although tcpdump does not show any incoming ARP response on 
> peth0. So the ARP
> responses are received by the interface, but get dropped before coming 
> to tcpdump or xenbr0.
> peth0 counters for errors are 0. In tcpdump for peth0 I can see the 
> outgoing ARP requests.
> The only incoming packets I see are broadcasts from other machines 
> (router adv, other
> machines' ARP reqs for different IP addresses, not related to the xen 
> box)
> Still clueless,
>    -Jens
>                                        
I "solved" the problem ...
The xen machine has 4 ethernet devices:
04:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5708 
Gigabit Ethernet (rev 11)
08:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5708 
Gigabit Ethernet (rev 11)
0b:00.0 Ethernet controller: Intel Corporation 82571EB Gigabit Ethernet 
Controller (rev 06)
0b:00.1 Ethernet controller: Intel Corporation 82571EB Gigabit Ethernet 
Controller (rev 06)
The problem vanished when switching from the Broadcom interface (eth0) 
to an Intel interface (eth2)
as the physical device. I'm now running with peth2 on the xenbr0 bridge 
and it runs fine.
I'm not a kernel guru, but seems that the driver for the broadcom nic 
(bnx2) has some bug.
Cheers,
   -Jens

--
Dipl.-Inform. Jens Fiedler
FhI FOKUS, Competence Center for NGNI
Tel.: +49 30 3463 7270
jens.fiedler@xxxxxxxxxxxxxxxxxxx 

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