RE: [Xen-users] a lot of packet loss

["Fischer, Anna" <anna.fischer@xxxxxx>]

Are you pinging between two different (remote?) DomUs, or between a DomU and a 
(remote?) Dom0 ? I don't see that from your description. Also, you should use 
tcpdump -i ethX to specify which network interface to trace on. Otherwise you 
will trace on the default interface, and I am not sure that is what you want 
(especially when tracing in Dom0).

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Attila Szamos
> Sent: 01 May 2009 16:15
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] a lot of packet loss
> 
> I commented out the resolv.conf, but nothing changed.
> I also tried the tcpdump issue. I experienced this:
> 
> root@test5:~# ping 172.27.68.28
> PING 172.27.68.28 (172.27.68.28) 56(84) bytes of data.
> 64 bytes from 172.27.68.28: icmp_seq=10 ttl=64 time=0.189 ms
> 64 bytes from 172.27.68.28: icmp_seq=11 ttl=64 time=0.218 ms
> 
> --- 172.27.68.28 ping statistics ---
> 16 packets transmitted, 2 received, 87% packet loss, time 15004ms
> rtt min/avg/max/mdev = 0.189/0.203/0.218/0.020 ms
> 
> 
> On the host:
> root@test6:~# cat dom0tcpdump > dom0tcpdump
> root@test6:~# cat dom0tcpdump | grep ICMP
> 01:03:19.108715 IP 172.27.68.114 > 172.27.68.28: ICMP echo request, id
> 7461, seq 10, length 64
> 01:03:19.108754 IP 172.27.68.28 > 172.27.68.114: ICMP echo reply, id
> 7461, seq 10, length 64
> 01:03:20.108733 IP 172.27.68.114 > 172.27.68.28: ICMP echo request, id
> 7461, seq 11, length 64
> 01:03:20.108770 IP 172.27.68.28 > 172.27.68.114: ICMP echo reply, id
> 7461, seq 11, length 64
> 
> On the guest:
> root@test-vm2:~# tcpdump > domutcp
> root@test-vm2:~# cat domutcp | grep ICMP
> 01:03:19.142677 IP 172.27.68.114 > 172.27.68.28: ICMP echo request, id
> 7461, seq 10, length 64
> 01:03:19.142677 IP 172.27.68.28 > 172.27.68.114: ICMP echo reply, id
> 7461, seq 10, length 64
> 01:03:20.108578 IP 172.27.68.114 > 172.27.68.28: ICMP echo request, id
> 7461, seq 11, length 64
> 01:03:20.108578 IP 172.27.68.28 > 172.27.68.114: ICMP echo reply, id
> 7461, seq 11, length 64
> 
> It is very interesting, because it seems that the ICMP packets even
> dont reach the host OS, but If I ping the host OS, each ICMP echo
> request got an ECHO reply.
> 
> I read about this network problem in another forums, and someone had
> the same problem. He tought it is scheduling problem.
> 
> 
> 
> 
> On Sat, May 2, 2009 at 12:49 AM, Bhasker C V <bhasker@xxxxxxxxxxxxx>
> wrote:
> > On Fri, 1 May 2009, Attila Szamos wrote:
> >
> >> I've fix-ed the timesyncronization problem. But I don't know where
> to
> >> start with the network problem.
> >> If I ping the VM a lot of packet didn't get an echo reply.
> >>
> >> root@test6:~# ping perftest-vm2
> >> PING test-vm2 (172.27.68.28) 56(84) bytes of data.
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=1 ttl=64 time=0.346
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=2 ttl=64 time=0.048
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=3 ttl=64 time=0.039
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=4 ttl=64 time=0.041
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=6 ttl=64 time=0.032
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=7 ttl=64 time=0.044
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=8 ttl=64 time=0.038
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=43 ttl=64 time=8.05
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=56 ttl=64 time=0.042
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=57 ttl=64 time=0.036
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=58 ttl=64 time=0.041
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=59 ttl=64 time=0.038
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=60 ttl=64 time=0.041
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=61 ttl=64 time=0.038
> ms
> >> 64 bytes from test-vm2 (172.27.68.28): icmp_seq=62 ttl=64 time=0.033
> ms
> >>
> >> --- test-vm2 ping statistics ---
> >> 64 packets transmitted, 15 received, 76% packet loss, time 63064ms
> >> rtt min/avg/max/mdev = 0.032/0.594/8.056/1.995 ms
> >
> > Does the ping directly to IP address too gives the same issue ?
> > sometimes DNS is a pain...
> > also on the domU side, try commenting out the complete resolv.conf
> > just to take DNS out of the way and try direct IP ping.
> >
> > you can also on the domU side run a tcpdump and check why the
> particular
> > icmp sequence number is missing. you can see the replies from domU
> and
> > if the reply does not come to the dom0, then there could be a problem
> with
> > xen.
> > else
> > ...
> >
> >>
> >> I've tried to switch the networking to 'route' from 'bridge', but it
> >> didn't help. Any suggestions?
> >>
> >> _______________________________________________
> >> Xen-users mailing list
> >> Xen-users@xxxxxxxxxxxxxxxxxxx
> >> http://lists.xensource.com/xen-users
> >>
> >
> > Bhasker C V
> > Registered linux user #306349
> >
> >
> >
> 
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> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users

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