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Old 08-22-2012, 01:01 PM
Richard Reina
 
Default Centos machine sometimes unreachable

I have a simple perl script that every few hours pings the handful of
machines on my LAN. Lately I've sometimes been getting

ping of 192.168.0.1 succeeded
ping of 192.168.0.7 succeeded
ping of 192.168.0.5 FAILED
ping of 192.168.0.6 succeeded
ping of 192.168.0.9 succeeded

This machine in question has been running Centos faithfully for about six
years and no recent changes to it have been made. When I try and ping the
machine manually it works. /var/og/messages does not seem irregular. Does
anyone know know what might be the problem or what else I might check?


Thanks,

Richard
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Old 08-22-2012, 01:08 PM
Götz Reinicke
 
Default Centos machine sometimes unreachable

Am 22.08.12 15:01, schrieb Richard Reina:
> I have a simple perl script that every few hours pings the handful of
> machines on my LAN. Lately I've sometimes been getting
>
> ping of 192.168.0.1 succeeded
> ping of 192.168.0.7 succeeded
> ping of 192.168.0.5 FAILED
> ping of 192.168.0.6 succeeded
> ping of 192.168.0.9 succeeded
>
> This machine in question has been running Centos faithfully for about six
> years and no recent changes to it have been made. When I try and ping the
> machine manually it works. /var/og/messages does not seem irregular. Does
> anyone know know what might be the problem or what else I might check?

Recently I was faced with a similar problem (cant ping a device from
time to time which was not touched for about two years...). My solution:
check the lan cabel.

The system I had problems with had been standing in the sun behind a
window and the lan cabel was 'melting' and did not fit properly into the
adapter.

my2cents.


--
Götz Reinicke . Filmakademie Baden-Württemberg GmbH


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Old 08-22-2012, 01:16 PM
 
Default Centos machine sometimes unreachable

Richard Reina wrote:
> I have a simple perl script that every few hours pings the handful of
> machines on my LAN. Lately I've sometimes been getting
>
> ping of 192.168.0.1 succeeded
> ping of 192.168.0.7 succeeded
> ping of 192.168.0.5 FAILED
> ping of 192.168.0.6 succeeded
> ping of 192.168.0.9 succeeded
>
> This machine in question has been running Centos faithfully for about
> six years and no recent changes to it have been made. When I try and
ping the
> machine manually it works. /var/og/messages does not seem irregular.
> Does anyone know know what might be the problem or what else I might check?

Have you done an ifconfig on 5, and seen if there's any collisions, etc?
Another possibility is that *you* haven't changed, but someone else has
put a piece of hardware on the LAN that's trying to get that IP, or has it
configured for that IP.

mark, who *really* wishes that the network folks would give
their hardware IPs by MAC, not broadcast

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Old 08-22-2012, 01:20 PM
 
Default Centos machine sometimes unreachable

Götz Reinicke wrote:
> Am 22.08.12 15:01, schrieb Richard Reina:
>> I have a simple perl script that every few hours pings the handful of
>> machines on my LAN. Lately I've sometimes been getting
>>
>> ping of 192.168.0.1 succeeded
>> ping of 192.168.0.7 succeeded
>> ping of 192.168.0.5 FAILED
>>
>> This machine in question has been running Centos faithfully for about
>> six years and no recent changes to it have been made. When I try and ping
<snip>
> Recently I was faced with a similar problem (cant ping a device from
> time to time which was not touched for about two years...). My solution:
> check the lan cabel.
>
> The system I had problems with had been standing in the sun behind a
> window and the lan cabel was 'melting' and did not fit properly into the
> adapter.

Good thought! Could someone have moved non-computer hardware, like, say, a
desk or chair, or there's been some utility work, and the cable run's
impacted occasionally... or stepped on?

mark

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Old 08-22-2012, 01:20 PM
Giles Coochey
 
Default Centos machine sometimes unreachable

On 22/08/2012 14:01, Richard Reina wrote:

I have a simple perl script that every few hours pings the handful of
machines on my LAN. Lately I've sometimes been getting

ping of 192.168.0.1 succeeded
ping of 192.168.0.7 succeeded
ping of 192.168.0.5 FAILED
ping of 192.168.0.6 succeeded
ping of 192.168.0.9 succeeded

This machine in question has been running Centos faithfully for about six
years and no recent changes to it have been made. When I try and ping the
machine manually it works. /var/og/messages does not seem irregular. Does
anyone know know what might be the problem or what else I might check?



I had this problem in the past and found that it seemed to be due to
iCMP rate limiting. We were pinging a lot of hosts from the monitoring
system, however... But you might want to investigate here:
http://www.kernel.org/doc/man-pages/online/pages/man7/icmp.7.html


--
Regards,

Giles Coochey, CCNA, CCNAS
NetSecSpec Ltd
+44 (0) 7983 877438
http://www.coochey.net
http://www.netsecspec.co.uk
giles@coochey.net


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Old 08-22-2012, 07:23 PM
Richard Reina
 
Default Centos machine sometimes unreachable

Look like there are some errors although I am not sure what the mean.

eth0 Link encap:Ethernet HWaddr 000:B7:5A:C6:FE
inet addr:192.168.0.5 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::2d0:b7ff:fe5a:c6fe/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2316067887 errors:0 dropped:0 overruns:1 frame:1
TX packets:2451037674 errors:3 dropped:0 overruns:0 carrier:3
collisions:0 txqueuelen:1000
RX bytes:221599111550 (206.3 GiB) TX bytes:575914174697 (536.3
GiB)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:1197938537 errors:0 dropped:0 overruns:0 frame:0
TX packets:1197938537 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:109601534433 (102.0 GiB) TX bytes:109601534433 (102.0
GiB)

Cable seems fine and machine is in a dark room (no sunlight) although it
does run through the ceiling.


2012/8/22 <m.roth@5-cent.us>

> Richard Reina wrote:
> > I have a simple perl script that every few hours pings the handful of
> > machines on my LAN. Lately I've sometimes been getting
> >
> > ping of 192.168.0.1 succeeded
> > ping of 192.168.0.7 succeeded
> > ping of 192.168.0.5 FAILED
> > ping of 192.168.0.6 succeeded
> > ping of 192.168.0.9 succeeded
> >
> > This machine in question has been running Centos faithfully for about
> > six years and no recent changes to it have been made. When I try and
> ping the
> > machine manually it works. /var/og/messages does not seem irregular.
> > Does anyone know know what might be the problem or what else I might
> check?
>
> Have you done an ifconfig on 5, and seen if there's any collisions, etc?
> Another possibility is that *you* haven't changed, but someone else has
> put a piece of hardware on the LAN that's trying to get that IP, or has it
> configured for that IP.
>
> mark, who *really* wishes that the network folks would give
> their hardware IPs by MAC, not broadcast
>
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
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CentOS@centos.org
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Old 08-22-2012, 08:00 PM
 
Default Centos machine sometimes unreachable

Richard Reina wrote:
> Look like there are some errors although I am not sure what the mean.
>
> eth0 Link encap:Ethernet HWaddr 000:B7:5A:C6:FE
> inet addr:192.168.0.5 Bcast:192.168.0.255 Mask:255.255.255.0
> inet6 addr: fe80::2d0:b7ff:fe5a:c6fe/64 Scope:Link
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:2316067887 errors:0 dropped:0 overruns:1 frame:1
> TX packets:2451037674 errors:3 dropped:0 overruns:0 carrier:3
> collisions:0 txqueuelen:1000
> RX bytes:221599111550 (206.3 GiB) TX bytes:575914174697 (536.3
> GiB)
>
> Cable seems fine and machine is in a dark room (no sunlight) although it
> does run through the ceiling.
>
Please stop top posting.

I'm not sure, but overrun? Frame? Not sure. Cabling goes into the
ceiling... was there any wiring or HVAC work done lately, where the cables
might run?

mark
>
> 2012/8/22 <m.roth@5-cent.us>
>
>> Richard Reina wrote:
>> > I have a simple perl script that every few hours pings the handful of
>> > machines on my LAN. Lately I've sometimes been getting
>> >
>> > ping of 192.168.0.1 succeeded
>> > ping of 192.168.0.7 succeeded
>> > ping of 192.168.0.5 FAILED
>> > ping of 192.168.0.6 succeeded
>> > ping of 192.168.0.9 succeeded
>> >
>> > This machine in question has been running Centos faithfully for
>> about
>> > six years and no recent changes to it have been made. When I try and
>> ping the
>> > machine manually it works. /var/og/messages does not seem irregular.
>> > Does anyone know know what might be the problem or what else I might
>> check?
>>
>> Have you done an ifconfig on 5, and seen if there's any collisions, etc?
>> Another possibility is that *you* haven't changed, but someone else has
>> put a piece of hardware on the LAN that's trying to get that IP, or has
>> it
>> configured for that IP.
>>
>> mark, who *really* wishes that the network folks would give
>> their hardware IPs by MAC, not broadcast
>>
>> _______________________________________________
>> CentOS mailing list
>> CentOS@centos.org
>> http://lists.centos.org/mailman/listinfo/centos
>>
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>


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Old 08-22-2012, 08:22 PM
Les Mikesell
 
Default Centos machine sometimes unreachable

On Wed, Aug 22, 2012 at 8:01 AM, Richard Reina <gatorreina@gmail.com> wrote:
> I have a simple perl script that every few hours pings the handful of
> machines on my LAN. Lately I've sometimes been getting
>
> ping of 192.168.0.1 succeeded
> ping of 192.168.0.7 succeeded
> ping of 192.168.0.5 FAILED
> ping of 192.168.0.6 succeeded
> ping of 192.168.0.9 succeeded
>
> This machine in question has been running Centos faithfully for about six
> years and no recent changes to it have been made. When I try and ping the
> machine manually it works. /var/og/messages does not seem irregular. Does
> anyone know know what might be the problem or what else I might check?
>

What does ethtool say about your duplex setting, and is the connected
switch set one way or the other? In the long distant past, cisco
switches weren't very good about negotiating and they recommended
configuring full duplex at both ends of the connections. Now the
hardware and standards are better and everyone uses auto, but you
might have an old switch or an old configuration somewhere in the
path. The problem is that if one end of the connection is set to not
negotiate, the other end will pick half duplex and the mismatch will
cause trouble at random.

--
Les Mikesell
lesmikesell@gmail.com
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Old 08-22-2012, 08:55 PM
Spiro Harvey
 
Default Centos machine sometimes unreachable

On Wed, 22 Aug 2012 16:00:45 -0400
m.roth@5-cent.us wrote:

> Richard Reina wrote:
> > Look like there are some errors although I am not sure what the
> > mean.
> >
> > eth0 Link encap:Ethernet HWaddr 000:B7:5A:C6:FE
> > inet addr:192.168.0.5 Bcast:192.168.0.255
> > Mask:255.255.255.0 inet6 addr: fe80::2d0:b7ff:fe5a:c6fe/64
> > Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> > RX packets:2316067887 errors:0 dropped:0 overruns:1
> > frame:1 TX packets:2451037674 errors:3 dropped:0 overruns:0
> > carrier:3 collisions:0 txqueuelen:1000
> > RX bytes:221599111550 (206.3 GiB) TX bytes:575914174697
> > (536.3 GiB)
> >
> > Cable seems fine and machine is in a dark room (no sunlight)
> > although it does run through the ceiling.
> >
> Please stop top posting.

People in glass houses shouldn't throw stones. Complaining about top
posting and then not trimming everything you're not replying to
(like below) is just as bad...


> I'm not sure, but overrun? Frame? Not sure. Cabling goes into the
> ceiling... was there any wiring or HVAC work done lately, where the
> cables might run?
>
> mark
> >
> > 2012/8/22 <m.roth@5-cent.us>
> >
> >> Richard Reina wrote:
> >> > I have a simple perl script that every few hours pings the
> >> > handful of machines on my LAN. Lately I've sometimes been getting
> >> >
> >> > ping of 192.168.0.1 succeeded
> >> > ping of 192.168.0.7 succeeded
> >> > ping of 192.168.0.5 FAILED
> >> > ping of 192.168.0.6 succeeded
> >> > ping of 192.168.0.9 succeeded
> >> >
> >> > This machine in question has been running Centos faithfully for
> >> about
> >> > six years and no recent changes to it have been made. When I try
> >> > and
> >> ping the
> >> > machine manually it works. /var/og/messages does not seem
> >> > irregular. Does anyone know know what might be the problem or
> >> > what else I might
> >> check?
> >>
> >> Have you done an ifconfig on 5, and seen if there's any
> >> collisions, etc? Another possibility is that *you* haven't
> >> changed, but someone else has put a piece of hardware on the LAN
> >> that's trying to get that IP, or has it
> >> configured for that IP.
> >>
> >> mark, who *really* wishes that the network folks would give
> >> their hardware IPs by MAC, not broadcast
> >>
> >> _______________________________________________
> >> CentOS mailing list
> >> CentOS@centos.org
> >> http://lists.centos.org/mailman/listinfo/centos
> >>
> > _______________________________________________
> > CentOS mailing list
> > CentOS@centos.org
> > http://lists.centos.org/mailman/listinfo/centos
> >
>
>
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos


--
Spiro Harvey Knossos Networks Ltd
(04) 460-2531 : (021) 295-1923 www.knossos.net.nz
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Old 08-23-2012, 06:45 PM
Richard Reina
 
Default Centos machine sometimes unreachable

2012/8/22 Les Mikesell <lesmikesell@gmail.com>

> On Wed, Aug 22, 2012 at 8:01 AM, Richard Reina <gatorreina@gmail.com>
> wrote:
> > I have a simple perl script that every few hours pings the handful of
> > machines on my LAN. Lately I've sometimes been getting
> >
> > ping of 192.168.0.1 succeeded
> > ping of 192.168.0.7 succeeded
> > ping of 192.168.0.5 FAILED
> > ping of 192.168.0.6 succeeded
> > ping of 192.168.0.9 succeeded
> >
> > This machine in question has been running Centos faithfully for about
> six
> > years and no recent changes to it have been made. When I try and ping the
> > machine manually it works. /var/og/messages does not seem irregular.
> Does
> > anyone know know what might be the problem or what else I might check?
> >
>
> What does ethtool say about your duplex setting


Here is the output from ethtool

Settings for eth0:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: MII
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: g
Current message level: 0x00000007 (7)
Link detected: yes

THe switch is a linksys etherfast 3124 that has worked perfectly for 10
years. I don't know anything about it's settings. This is a LAN with about
a dozen machines.

Thanks
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