Moritz,
I am seeing something very similar - see 
http://lists.xensource.com/archives/html/xen-devel/2008-09/msg00686.html
It looks as though the responses to arp requests are being dropped by the 
bridge, causing a halt in packet forwarding. Interestingly, the packet drop 
occurs even if I manually fill in the arp table with the entry. I am running 
with xen-unstable c/s 18242.
Phil
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel- 
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Moritz Möller
> Sent: Friday, September 19, 2008 11:59 AM
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] bridge + arp
>
> Hi,
>
> this is propably bridge related and not really a xen problem, but it
> might help someone:
>
> Some of our domUs are not able to arp. Arp -n show (incomplete), and
> doing a tcpdump shows, that on the dom0's eth0 the arp request goes out,
> the response comes in, but on the vifX.0 interface the arp response is
> gone.
>
> dom0# tcpdump -ni eth0
> arp who-has 10.32.2.51 tell 10.32.7.70
> arp reply 10.32.2.51 is-at 00:30:48:34:44:6c
>
> dom0# tcpdump -ni br0
> arp who-has 10.32.2.51 tell 10.32.7.70
> arp reply 10.32.2.51 is-at 00:30:48:34:44:6c
>
> dom0# tcpdump -ni vif3.0
> arp who-has 10.32.2.51 tell 10.32.7.70
>
> Does someone know why the dom0 br0 or vif eats the arp response?
>
> Thanks a lot,
>
> Moritz
>
>
> ip a l
> 1: lo: <LOOPBACK,UP,10000> mtu 16436 qdisc noqueue
> link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
> inet 127.0.0.1/8 scope host lo
> inet6 ::1/128 scope host
> valid_lft forever preferred_lft forever
> 2: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen
> 1000
> link/ether 00:30:48:34:13:dc brd ff:ff:ff:ff:ff:ff
> inet6 fe80::230:48ff:fe34:13dc/64 scope link
> valid_lft forever preferred_lft forever
> 3: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop qlen 1000
> link/ether 00:30:48:34:13:dd brd ff:ff:ff:ff:ff:ff
> 4: br0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue qlen 20000
> link/ether 00:30:48:34:13:dc brd ff:ff:ff:ff:ff:ff
> inet 10.32.2.50/14 brd 10.35.255.255 scope global br0
> inet6 fe80::230:48ff:fe34:13dc/64 scope link
> valid_lft forever preferred_lft forever
> 5: vif1.0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen
> 32
> link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
> inet6 fe80::fcff:ffff:feff:ffff/64 scope link
> valid_lft forever preferred_lft forever
> 6: vif2.0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen
> 32
> link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
> inet6 fe80::fcff:ffff:feff:ffff/64 scope link
> valid_lft forever preferred_lft forever
> 7: vif3.0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen
> 32
> link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
> inet6 fe80::fcff:ffff:feff:ffff/64 scope link
> valid_lft forever preferred_lft forever
>
>
> brctl show
> bridge name bridge id STP enabled interfaces
> br0 8000.0030483413dc no eth0
> vif1.0
> vif2.0
> vif3.0
>
>
>
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