[CentOS] strange network problem

Juan Carlos Díaz Fernández juan.carlos.diaz at ign-solutions.com
Fri Mar 5 15:01:04 UTC 2010


Hello,

Are your netmask config Ok? Can you use wireshark to sniff traffic in the
middle LANCOM <->Wireshark/tcpdump<->Xenserver and send me a trace?

Best Regards,

Juan Carlos Díaz Fernández
IGN Solutions™
Director Técnico
mailto: juan.carlos.diaz at ign-solutions.com
callto: +34638295207/+34617413903

Innova Galicia Networks Solutions SL
http://www.ign-solutions.com
Pazo de Feiras e Congresos de Lugo - Palomar s/n
27004 LUGO - Spain
callto: +34982284150 faxto: +34982284922


2010/3/5 Michael Schumacher <michael.schumacher at pamas.de>

>
> Nobody having an idea?
>
> > Hi,
> > I am trying to fix a problem I have for about a week now.
> > The environment is:
> > --several independent servers with Centos5.4 on the latest patchlevel
> > (example will be server2) All of them are working properly.
> > --a machine with Xen installed to host some virtual machines
> > (xenserver1)
> > --domu servers on xenserver1 (crmserver1, winserver1)
>
> > The whole network is connected with a Lancom router to a DSL line.
>
> > Some days ago I noticed that server2 was updated properly, but
> > xenserver1, crmserver1 and winserver were not updating the OS
> > properly. They seemed to be cut off the internet. I can ping from all
> > to all servers internally, I can ssh from all to  all servers
> > internally and I can browse the Internet from server2 successfully
> > (using IP-numbers and hostnames), but xenserver1 and its domu clients
> > could not connect to the internet. I checked the firewalls on
> > xenserver, and crmserver1. They seemed to be OK and stopping them with
> > "etc/init.d/iptables stop" didn't solve the problem.
>
> > I can resolve hostnames:
>
> >>[root at xenserver1 ~]# nslookup www.centos.org
> >>Server:         192.168.1.1
> >>Address:        192.168.1.1#53
> >>
> >>Non-authoritative answer:
> >>Name:   www.centos.org
> >>Address: 72.232.194.162
>
> > but I cannot browse neither to "elinks http://www.centos.org" nor to
> > 72.232.194.162, however, I can ping www.centos.org successfully.
>
>
> > the network routes seem to be OK :
>
> >>[root at xenserver1 ~]# route
> >>Kernel IP routing table
> >>Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> >>10.1.1.0        *               255.255.255.0   U     0      0        0
> eth1
> >>192.168.122.0   *               255.255.255.0   U     0      0        0
> virbr0
> >>169.254.0.0     *               255.255.0.0     U     0      0        0
> eth0
> >>192.168.0.0     *               255.255.0.0     U     0      0        0
> eth0
> >>default         LANCOM_1751_1.p 0.0.0.0         UG    0      0        0
> eth0
>
> > (eth1 is a drbd interface)
>
> >> [root at crmserver1 ~]# route
> >> Kernel IP routing table
> >> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> >> 169.254.0.0     *               255.255.0.0     U     0      0        0
> eth0
> >> 192.168.0.0     *               255.255.0.0     U     0      0        0
> eth0
> >> default         LANCOM_1751_1.p 0.0.0.0         UG    0      0        0
> eth0
>
>
>
> > Has anybody any clue where to look?
>
> best regards
> ---
> Michael Schumacher
>
>
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>
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