Re: [tlug] network losing connection

[Matt Gross <mgrossjp@??>]

On Tue, 2007-02-27 at 21:04 +0900, Uva Coder wrote:
> On 2/27/07, Godwin Stewart <godwin.stewart@??> wrote:
> >
> > What Sigurd said about checking the "error" number on your ifconfig
> > output is a good start. Bear in mind that this could also have a simple
> > answer like a bad cable...
> 
> Good point.
> 
> Besides checking the logs, running ipconfig, and checking the cable, do:
> Check connection to route (i.e ping the router)

when everything is working: 

[root@?? log]# ping 192.168.0.254
PING 192.168.0.254 (192.168.0.254) 56(84) bytes of data.
64 bytes from 192.168.0.254: icmp_seq=1 ttl=64 time=0.182 ms
64 bytes from 192.168.0.254: icmp_seq=2 ttl=64 time=0.176 ms
64 bytes from 192.168.0.254: icmp_seq=3 ttl=64 time=0.170 ms
64 bytes from 192.168.0.254: icmp_seq=4 ttl=64 time=0.212 ms
64 bytes from 192.168.0.254: icmp_seq=5 ttl=64 time=0.193 ms

--- 192.168.0.254 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3999ms
rtt min/avg/max/mdev = 0.170/0.186/0.212/0.021 ms

when not working:

[root@?? log]# ping 192.168.0.254
PING 192.168.0.254 (192.168.0.254) 56(84) bytes of data.
From 192.168.0.246 icmp_seq=2 Destination Host Unreachable
From 192.168.0.246 icmp_seq=3 Destination Host Unreachable
From 192.168.0.246 icmp_seq=6 Destination Host Unreachable
From 192.168.0.246 icmp_seq=8 Destination Host Unreachable
From 192.168.0.246 icmp_seq=9 Destination Host Unreachable
From 192.168.0.246 icmp_seq=12 Destination Host Unreachable
From 192.168.0.246 icmp_seq=13 Destination Host Unreachable

--- 192.168.0.254 ping statistics ---
13 packets transmitted, 0 received, +7 errors, 100% packet loss, time
12000ms
, pipe 2


> Check your routing table for errors (i.e. netstat -nr)

when working:

[root@?? log]# netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt
Iface
192.168.0.0     0.0.0.0         255.255.255.0   U         0 0          0
eth1
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0
eth1
0.0.0.0         192.168.0.254   0.0.0.0         UG        0 0          0
eth1


when not working:

[root@?? log]# netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt
Iface
192.168.0.0     0.0.0.0         255.255.255.0   U         0 0          0
eth1
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0
eth1
0.0.0.0         192.168.0.254   0.0.0.0         UG        0 0          0
eth1



> Check your arp table for errors (i.e. arp -a)

when working:

[root@?? log]# arp -a
? (192.168.0.254) at 00:90:CC:42:71:58 [ether] on eth1


when not working:

[root@?? log]# arp -a
? (192.168.0.254) at <incomplete> on eth1

> 
> If no problems above, then we need a better understanding of your
> machine. Here's a shotgun approach:
> Which SELinux setting are you using?
/etc/sysconfig/selinux:

SELINUX=disabled
SELINUXTYPE=targeted
SETLOCALDEFS=0 

> Have you modified your SELinux configuration otherwise?

No

> Did you change anything recently? ;-) (i.e. changed a router setting,
> proxy setting, ect.)

I have not made any changes other than yum updates (maybe the problem is
here?)

> What applications are running on the server? (i.e. apache, bind,
> sendmail, squid, JBoss, ect.)

sendmail, apache, mysql, gtk-gnutella, aMSN, evolution, mysql, and many
others.  This is a recent problem though (last week or week and a half)

> Which kernel version are you running?

x86_64 2.6.19-1.2911.fc6

> What is the network card(s)/chipset(s) you are using?

I have a MSI K9N Diamond motherboard:  

"On-board LAN: Yes, two Gigabit Ethernet controlled by the chipset
together with two Vitesse SimplyPHY chips (VSC8601) chips."
http://www.hardwaresecrets.com/article/400/3

> Are you using wireless networking device in conjuction with a network
> interface card?

No wireless networking being used.

> 
> Some of the questions above came from common fedora 6 issues that I've
> read. To answer your earlier questions, yes but I'd rather begin with
> the suggestions above before going there.

I find this to be a very strange problem.  If I do a "ifdown eth1 &&
ifup eth1" the connection comes back up for anywhere from 15 seconds to
a few minutes.  But the length of time is inconsistent.

I performed a tcpdump -XXvv and noticed a few things.  There were a lot
of entries similar to the following with the "bad udp cksum":

20:16:33.494112 IP (tos 0x0, ttl  64, id 47214, offset 0, flags [DF],
proto: UDP (17), length: 71) fedora6.48225 > wtk-ns03.usen.ad.jp.domain:
[bad udp cksum 29eb!]  36173+ PTR? 1.112.122.61.in-addr.arpa. (43)

20:16:34.406371 IP (tos 0x0, ttl  64, id 58126, offset 0, flags [DF],
proto: UDP (17), length: 66) fedora6.48227 > wtk-ns03.usen.ad.jp.domain:
[bad udp cksum e0cb!]  11102+ AAAA? pop.mail.yahoo.co.jp. (38)

20:16:34.604046 IP (tos 0x0, ttl  64, id 33916, offset 0, flags [DF],
proto: TCP (6), length: 72) fedora6.58821 > cs57.msg.dcn.yahoo.com.mmcc:
P, cksum 0x5c2d (incorrect (-> 0x2f95), 2906:2926(20) ack 3727 win 574
<nop,nop,timestamp 72999891 1894641182>

Is this normal?

This problem is so painful, I am debating doing a full re-install in
hopes of fixing everything.  Would you discourage/recommend that I do
this?

I really appreciate everyone's input and help with this.  Thanks again!

> 
> Regards,
> Uva
>

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