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xen-users
Re: [Xen-users] network problems
Mike Lovell wrote:
So, I have been running into network problems for a while on 4 boxes
that I installed xen on so that some engineers have places to test
code. This particular problem is happening on all 4 of these boxes.
(although, it isn't happening on an older box running xen from debian
etch).
What appears to be the problem is that traffic is getting dropped
between the vif#.0 interface in dom0 and the eth0 interface in the
guest. To find this out, I started a ping flood from one domU that was
pinging another domU. About every 10 minutes, there will be a lot of
ping requests going out but no replies coming back. I think it really
weird that it happens like ever 10 minutes plus about 2 seconds. While
the ping was going, I did tcpdumps from the domU starting the ping,
from the vif#.0 of the pinging machine, from the virtual bridge, from
the vif#.0 for the receiving guest, and then from the receiving domU.
The packets are making it all the way to the dom0 vif for the
receiving guest but not making it to the eth0 in the guest. I have no
clue why this is happening and it happens in rather regular intervals.
The same thing happens in pinging a different guest and it happens in
about the same interval but at different times. Also, during the ping
flood, there is never a pause in the sending of packets out of the
guest. Only a pause on the packets going from the host to the guest.
I am running this on 64 bit Debian Lenny using the distribution's
packages. xen-hypervisor-3.2-1-amd64 version 3.2.1-2 and
linux-image-2.6.26-2-xen-amd64 version 2.6.26-17. Here are the
networking configs.
---------
dom0# cat /etc/network/interfaces
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto eth0
iface eth0 inet static
address 10.135.7.34
netmask 255.255.255.224
network 10.135.7.32
broadcast 10.135.7.63
gateway 10.135.7.33
# dns-* options are implemented by the resolvconf package, if
installed
dns-nameservers 10.135.7.34
dns-search qa1.mozyops.com
auto vmnet
iface vmnet inet static
address 10.135.2.71
netmask 255.255.255.224
bridge_ports eth1
# bridge_stp off
# bridge_fd 9
# bridge_hello 2
# bridge_maxage 12
---------
DomU# cat /etc/network/interfaces
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto eth0
iface eth0 inet dhcp
post-up ethtool -K eth0 tx off
---------
Dom0# brctl show vmnet
bridge name bridge id STP enabled interfaces
vmnet 8000.003048c8166d no eth1
vif1.0
vif10.0
<other interfaces>
---------
Does anyone have any ideas as to what is going on here? Or more
importantly, any ideas on how to solve this? I have tried building a
newer domU kernel from scratch but I haven't been able to make any
progress there. The guest fails to boot without showing anything on
the console. It then goes into this loop of trying to reboot the guest
but failing. I would really like to stay with the debian kernels.
I have been banging my head against a wall for a week or so on this
and desperately need some help to get this working. I have engineers
that are getting held up by this bug.
This problem still exists.
I tried setting an independent wallclock on all of the virtual machines.
I also managed to miss that I had the wrong netmask configured for the
vmnet bridge. It should have been 255.255.255.128. The vms were able to
talk to each other before changing the netmask and I saw traffic flowing
past the switch.
Does anyone have any clue as to what might be going on? I am great need
of some help here.
Thanks
mike
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