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Old 03-04-2010, 10:00 AM
Michael Schumacher
 
Default strange network problem

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@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@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@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
PAMAS Partikelmess- und Analysesysteme GmbH
Dieselstr.10, D-71277 Rutesheim
Tel +49-7152-99630
Fax +49-7152-996333
GeschńftsfŘhrer: Gerhard Schreck
Handelsregister B Stuttgart HRB 252024

_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 03-05-2010, 12:00 PM
Michael Schumacher
 
Default strange network problem

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@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@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@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


_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 03-07-2010, 04:45 PM
Michael Schumacher
 
Default strange network problem

Dear Juan Carlos,

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

I couldn't make any further tests on that machine because I couldn't
install any software on that machine because of the failing network.
However, I took the opportunity and rebooted the machine last night.
Guess what, everything is up and running again.
Thanks for your assistance and sorry to the list for the disappeared
problem.
Reboot was no option through the week as this is a production machine
under heavy load.



--
Mit freundlichen GrŘ▀en
Michael Schumacher
mailto:michael.schumacher@pamas.de


_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 03-09-2010, 09:31 AM
Michael Schumacher
 
Default strange network problem

Dear Juan Carlos,

On Monday, March 8, 2010 you wrote:

> I hope your problem won't be a regular issue and you don't see it again.

I don't expect to see it again soon. The machine runs rock solid for a
year now without any trouble. Years ago, it happened from time to time
that services just died after some time (months?), but I think this
doesn't happen any longer. I don't know if this comes from the more
decent hardware we are using these days or from better software.

> All of the servers I've installed have a few tools by default to make tests
> in this cases (tcpdump (wireshark if gui), iptraf,
> iptables/pf,netcat,sysinternals(windows),...) and have a monitoring packages
> (Nagios/Ntop) in other machine to obtain data.

Sounds like a good idea. I will put some tools on the machines.

again, thanks for your help!


best regards
---
Michael Schumacher
PAMAS Partikelmess- und Analysesysteme GmbH
Dieselstr.10, D-71277 Rutesheim
Tel +49-7152-99630
Fax +49-7152-996333
GeschńftsfŘhrer: Gerhard Schreck
Handelsregister B Stuttgart HRB 252024

_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 09-07-2010, 02:49 AM
ŔĚ»
 
Default strange network problem

Hi ,everybody┬*┬*┬* ┬* ┬* ┬* I've met a strang network problem.My gentoo Netbook can't access google and some other web sites after ┬*lying idle about more than half an hour's. But it can acesses ┬*other sites normally ,And can pinging ┬*ervery sites including google very well! The Only thing i can do is rebooting ┬*the system,and Network resume aftre that. I've googled a lot,and found nothing to solve this problem. :-(┬*┬*┬* ┬* ┬* It borthered me a lot.Please help me!


ŠéĘŠâ│ŠőąŠťëňĺŊśôňůŹŔ┤╣Úé«š«▒ńŞÇŠ*Ěň╝║ňĄžšÜäŔŻ »ń╗ÂňÉŚ´╝č
 
Old 09-07-2010, 07:28 AM
Maciej Grela
 
Default strange network problem

2010/9/7 ŔĚ» <xaoru2001@163.com>:
> Hi ,everybody
> ┬*┬* ┬* ┬* ┬* I've met a strang network problem.My gentoo Netbook can't access
> google and some other web sites after ┬*lying idle about more than half an
> hour's. But it can acesses ┬*other sites normally ,And can pinging ┬*ervery
> sites including google very well! The Only thing i can do is rebooting ┬*the
> system,and Network resume aftre that. I've googled a lot,and found nothing
> to solve this problem. :-(
> ┬*┬* ┬* ┬* It borthered me a lot.Please help me!
>

You should run wireshark and see what is happening when you are trying
to access google.

Best regards,
Maciej Grela
 
Old 09-07-2010, 10:40 AM
Mick
 
Default strange network problem

On Tuesday 07 September 2010 08:28:32 Maciej Grela wrote:
> 2010/9/7 ŔĚ» <xaoru2001@163.com>:
> > Hi ,everybody
> > I've met a strang network problem.My gentoo Netbook can't access
> > google and some other web sites after lying idle about more than half an
> > hour's. But it can acesses other sites normally ,And can pinging ervery
> > sites including google very well! The Only thing i can do is rebooting
> > the system,and Network resume aftre that. I've googled a lot,and found
> > nothing to solve this problem. :-(
> > It borthered me a lot.Please help me!
>
> You should run wireshark and see what is happening when you are trying
> to access google.

If you can ping, but not resolve domain names then it could have something to
do with the DNS servers that you or your ISP are using.
--
Regards,
Mick
 
Old 09-07-2010, 11:00 AM
Alan McKinnon
 
Default strange network problem

Apparently, though unproven, at 12:40 on Tuesday 07 September 2010, Mick did
opine thusly:

> On Tuesday 07 September 2010 08:28:32 Maciej Grela wrote:
> > 2010/9/7 ŔĚ» <xaoru2001@163.com>:
> > > Hi ,everybody
> > >
> > > I've met a strang network problem.My gentoo Netbook can't
> > > access
> > >
> > > google and some other web sites after lying idle about more than half
> > > an hour's. But it can acesses other sites normally ,And can pinging
> > > ervery sites including google very well! The Only thing i can do is
> > > rebooting
> > >
> > > the system,and Network resume aftre that. I've googled a lot,and found
> > >
> > > nothing to solve this problem. :-(
> > >
> > > It borthered me a lot.Please help me!
> >
> > You should run wireshark and see what is happening when you are trying
> > to access google.
>
> If you can ping, but not resolve domain names then it could have something
> to do with the DNS servers that you or your ISP are using.

If he can ping www.google.com then his domain resolution must be working fine.



--
alan dot mckinnon at gmail dot com
 
Old 09-07-2010, 01:51 PM
ŔĚ»
 
Default strange network problem

At┬*2010-09-07´╝î"Alan┬*McKinnon"┬*<alan.mckinnon@gmail.com>┬* wrote:

>Apparently,┬*though┬*unproven,┬*at┬*12:40┬*on┬*Tu esday┬*07┬*September┬*2010,┬*Mick┬*did┬*
>opine┬*thusly:
>
>>┬*On┬*Tuesday┬*07┬*September┬*2010┬*08:28:32┬*Ma ciej┬*Grela┬*wrote:
>>┬*>┬*2010/9/7┬*ŔĚ»┬*<xaoru2001@163.com>:
>>┬*>┬*>┬*Hi┬*,everybody
>>┬*>┬*>┬*
>>┬*>┬*>┬*┬*┬*┬*┬*┬*┬*┬*┬*┬*I've┬*met┬*a┬*strang┬* network┬*problem.My┬*gentoo┬*Netbook┬*can't
>>┬*>┬*>┬*┬*┬*┬*┬*┬*┬*┬*┬*┬*access
>>┬*>┬*>┬*
>>┬*>┬*>┬*google┬*and┬*some┬*other┬*web┬*sites┬*af ter┬*┬*lying┬*idle┬*about┬*more┬*than┬*half
>>┬*>┬*>┬*an┬*hour's.┬*But┬*it┬*can┬*acesses┬*┬*ot her┬*sites┬*normally┬*,And┬*can┬*pinging┬*
>>┬*>┬*>┬*ervery┬*sites┬*including┬*google┬*very┬* well!┬*The┬*Only┬*thing┬*i┬*can┬*do┬*is
>>┬*>┬*>┬*rebooting
>>┬*>┬*>┬*
>>┬*>┬*>┬*┬*the┬*system,and┬*Network┬*resume┬*aftr e┬*that.┬*I've┬*googled┬*a┬*lot,and┬*found
>>┬*>┬*>┬*
>>┬*>┬*>┬*nothing┬*to┬*solve┬*this┬*problem.┬*:-(
>>┬*>┬*>┬*
>>┬*>┬*>┬*┬*┬*┬*┬*┬*┬*┬*It┬*borthered┬*me┬*a┬*lot. Please┬*help┬*me!
>>┬*>┬*
>>┬*>┬*You┬*should┬*run┬*wireshark┬*and┬*see┬*what ┬*is┬*happening┬*when┬*you┬*are┬*trying
>>┬*>┬*to┬*access┬*google.
>>┬*
>>┬*If┬*you┬*can┬*ping,┬*but┬*not┬*resolve┬*domain ┬*names┬*then┬*it┬*could┬*have┬*something
>>┬*to┬*do┬*with┬*the┬*DNS┬*servers┬*that┬*you┬*or ┬*your┬*ISP┬*are┬*using.
>
>If┬*he┬*can┬*ping┬*www.google.com┬*then┬*his┬*dom ain┬*resolution┬*must┬*be┬*working┬*fine.
>
>
>
>--┬*
>alan┬*dot┬*mckinnon┬*at┬*gmail┬*dot┬*com
>Thinks everyone: DNS woks well for me. i can ping www.google.com. Just can't access it in web-browsers without rebooting system.Sometimes I thought mybe it's the problem of Power.But now i doubt about it! Because even while I am watching videos online( about half an our) it happens.Here is the wireshark capture result: I don't know why there are so manay "RTS".Seq=0 Ack=1 Win=5672 Len=0 MSS=1430 TSV=1581039706 TSER=40437152 WS=6"
"32","14.006920","192.168.1.102","64.233.181.113", "TCP","57028 > http [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=40490336 TSER=0 WS=6"
"33","15.045762","64.233.181.113","192.168.1.102", "TCP","http > 57028 [SYN, ACK] Seq=0 Ack=1 Win=5672 Len=0 MSS=1430 TSV=3738233147 TSER=40437152 WS=6"
"34","15.045788","192.168.1.102","64.233.181.113", "TCP","57028 > http [RST] Seq=1 Win=0 Len=0"
"35","15.063001","64.233.181.113","192.168.1.102", "TCP","http > 57028 [SYN, ACK] Seq=0 Ack=1 Win=5672 Len=0 MSS=1430 TSV=3738233315 TSER=40437152 WS=6"
"36","15.063027","192.168.1.102","64.233.181.113", "TCP","57028 > http [RST] Seq=1 Win=0 Len=0"


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Old 09-07-2010, 02:12 PM
Florian CROUZAT
 
Default strange network problem

On 7 sept. 2010, at 15:51, ŔĚ» wrote:

> Thinks everyone:
> DNS woks well for me. i can ping www.google.com. Just can't access it in web-browsers without rebooting system.Sometimes I thought mybe it's the problem of Power.But now i doubt about it! Because even while I am watching videos online( about half an our) it happens.
> Here is the wireshark capture result: I don't know why there are so manay "RTS".
> Seq=0 Ack=1 Win=5672 Len=0 MSS=1430 TSV=1581039706 TSER=40437152 WS=6"
> "32","14.006920","192.168.1.102","64.233.181.113", "TCP","57028 > http [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=40490336 TSER=0 WS=6"
> "33","15.045762","64.233.181.113","192.168.1.102", "TCP","http > 57028 [SYN, ACK] Seq=0 Ack=1 Win=5672 Len=0 MSS=1430 TSV=3738233147 TSER=40437152 WS=6"
> "34","15.045788","192.168.1.102","64.233.181.113", "TCP","57028 > http [RST] Seq=1 Win=0 Len=0"
> "35","15.063001","64.233.181.113","192.168.1.102", "TCP","http > 57028 [SYN, ACK] Seq=0 Ack=1 Win=5672 Len=0 MSS=1430 TSV=3738233315 TSER=40437152 WS=6"
> "36","15.063027","192.168.1.102","64.233.181.113", "TCP","57028 > http [RST] Seq=1 Win=0 Len=0"

Since you are the one sending RESETs instead of ACKs, I'd use hping (hping -S -p 80 64.233.181.113) and check if the box also sends RESETs instead of ACKs using CLI, or with bash+nc :
( echo "GET / HTTP/1.0" ; echo ; echo "host:www.google.com" ; echo ) | nc 64.233.181.113 80
If you can actually read google sources using that, your browser is to blame, or a plugin ?

-----
Florian.
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